Uncategorized

Get PDF Chapter 004, Fields, Domains, and Individuals

Free download. Book file PDF easily for everyone and every device. You can download and read online Chapter 004, Fields, Domains, and Individuals file PDF Book only if you are registered here. And also you can download or read online all Book PDF file that related with Chapter 004, Fields, Domains, and Individuals book. Happy reading Chapter 004, Fields, Domains, and Individuals Bookeveryone. Download file Free Book PDF Chapter 004, Fields, Domains, and Individuals at Complete PDF Library. This Book have some digital formats such us :paperbook, ebook, kindle, epub, fb2 and another formats. Here is The CompletePDF Book Library. It's free to register here to get Book file PDF Chapter 004, Fields, Domains, and Individuals Pocket Guide.

The network address must be the last argument on the pntadm command line used to create, modify, or delete an IP address. Host name mapped to the IP address in the hosts table. This name may be automatically generated by DHCP Manager or interactive dhcpconfig when addresses are created. If you create a single address, you can supply the name. Macro the DHCP server uses to obtain network configuration options from the dhcptab. Several macros are created automatically when you configure a server and add networks.

See About Macros for more information about macros. When DHCP Manager or interactive dhcpconfig create addresses, they create a server macro and assign it as the configuration macro for each address. If the client ID is listed as 00, the address is not allocated to any client.

If you specify a client ID when modifying the properties of an IP address, you manually bind the address to that client for its exclusive use. For example, a Solaris client with the hexadecimal Ethernet address e would use the client ID E. Tip: As superuser on the Solaris client system, type the following command to obtain the Ethernet address for the interface: ifconfig -a. The setting that specifies the address is reserved exclusively for the client indicated by the client ID, and the DHCP server cannot reclaim the address. If you choose this option, you manually assign the address to the client.

A lease may be dynamic or permanent. See Dynamic and Permanent Lease Type for a complete explanation. Specify that the address would be permanently assigned with the -f option. Addresses are dynamically leased by default. Date and time when the lease expires, applicable only when a dynamic lease is specified. Before you add addresses, you must add the network that owns them to the DHCP service. The following figure shows the Create Address dialog box. The Duplicate Address dialog box is identical to the Create Address dialog box, except that the text fields display the values for an existing address.

The following figure shows the first dialog of the Address Wizard, used to add a range of IP addresses. See Table 4—6 for information about the settings. The Address Wizard prompts you to provide values for the IP address properties. See Table 4—6 for more information about the properties. Click the right arrow button as you finish entering information in each screen, and click Finish on the last screen.

Refer to the pntadm man page for a list of options you can use with pntadm -A. In addition, Table 4—6 shows some sample pntadm commands that specify options. You can write a script to add multiple addresses with pntadm. See Example 6—1 for an example. See the pntadm man page for more information about pntadm -M. The following figure shows the Address Properties dialog box that you use to modify IP address properties. The following figure shows the Modify Multiple Addresses dialog box that you use to modify multiple IP addresses.

If you want to modify more than one address, press the Control key while you click with the mouse to select multiple addresses. You can also press the Shift key while you click to select a block of addresses. Click the Help button or refer to Table 4—6 for information about the properties. Many options can be used with the pntadm command, which are documented in the pntadm man page.

Table 4—6 shows some sample pntadm commands that specify options. At times you might want the DHCP service to stop managing a particular address or group of addresses.

The Cognitive Self: The Self-Concept

The method you use to remove an address from DHCP depends on whether you want the change to be temporary or permanent. In DHCP Manager, you use the Address Properties dialog box, shown in Figure 4—10 , to mark individual addresses, and the Modify Multiple Addresses dialog box, show in Figure 4—11 , to mark multiple addresses, as described in the following procedure. If you want to mark more than one address unusable, press the Control key while you click with the mouse to select multiple addresses.

If you want to delete more than one address, press the Control key while you click with the mouse to select multiple addresses. If the host names were generated by DHCP Manager or dhcpconfig , you might want to delete the names from the hosts table. If you include the -y option, the host name is deleted from the name service in which it is maintained.

However, it is not always possible when a dynamic lease is used. Clients such as print or file servers should have consistent IP addresses as well, but can be set up to receive their network configurations through DHCP. You can set up a client to receive the same IP address each time it requests its configuration if you reserve, or manually assign, the client's ID to the address you want it to use.

You can set up the reserved address to use a dynamic lease to make it easy to track the use of the address, or a permanent lease if you do not need to track address use. However, you might not want to use permanent leases because once a client obtains a permanent lease, it does not contact the server again and cannot obtain updated configuration information unless it releases the IP address and restarts the DHCP lease negotiation. A diskless client is an example of a client that should use a reserved address with a dynamic lease.

The following figure shows the Lease tab of the Address Properties dialog box used to modify the lease. See the Client ID entry in Table 4—6 for more information. Select Dynamic if you want the client to negotiate to renew leases, and thus be able to track when the address is used. Because you selected Reserved, the address cannot be reclaimed even when it uses a dynamic lease.

You do not need to enter an expiration date for this lease. The DHCP server calculates the expiration date based on the lease time. If you select Permanent, you cannot track the use of the IP address unless you enable transaction logging. Refer to the Client ID entry in Table 4—6 for more information about how to determine client identifiers. DHCP Manager and dhcpconfig create a number of macros automatically when you configure the server.

You might find that when changes occur on your network, you need to make changes to the configuration information passed to clients. To do this, you need to work with DHCP macros. You can view, create, modify, duplicate, and delete DHCP macros. Change macros by modifying existing options, adding options to macros, removing options from macros. The Macros area on the left side of the window displays, in alphabetical order, all macros defined on the server.

Macros preceded by a folder icon include references to other macros, while macros preceded by a document icon do not reference other macros. To view the contents of a macro, click the macro name and look at the area on the right side of the window. This command prints to standard output the formatted contents of the dhcptab , including all macros and symbols defined on the server.

You might need to modify macros when some aspect of your network changes and one or more clients need to know about the change. For example, you might add a router or a NIS server, create a new subnet, or decide to change the lease policy. When you modify a macro, you must know the name of the DHCP option that corresponds to the parameter you want to change, add, or delete.

See the dhtadm man page for more information about dhtadm. This selection tells the DHCP server to reread the dhcptab to put the change into effect immediately after you click OK.

For example, to change the lease time and the Universal Time Offset in macro bluenote , type the following command:. Click the Select button next to the Option Name field and select the option you want to add to the macro. The Select Option dialog box displays an alphabetized list of names of Standard category options and descriptions.

If you want to add an option that is not in the Standard category, use the Category list to select the category you want. See About Macros for more information about macro categories. Type Include if you want to include a reference to an existing macro in the new macro. If you typed Include as the option name, you must specify the name of an existing macro in the Option Value field. The option is added to the bottom of the list of options displayed for this macro. If you want to change the option's position in the list, select the option and click the arrow keys next to the list to move the option up or down.

For example, to add the ability to negotiate leases, in macro bluenote , type the following command:. For example, to remove the ability to negotiate leases in macro bluenote , type the following command:. You may want to add new macros to your DHCP service to support clients with specific needs. See the dhtadm man page for more information about the dhtadm command.

The name can be up to alphanumeric characters. If you use a name that matches a vendor class identifier, network address, or client ID, the macro will be processed automatically for appropriate clients. If you use a different name, the macro can only be processed if it is assigned to a specific IP address or included in another macro that is processed.

The Select Option dialog box displays an alphabetized list of names of Standard category options and their descriptions. See About Options for more information about option categories. You might want to delete a macro from the DHCP service. For example, if you delete a network from the DHCP service, you can also delete the associated network macro.

Options are keywords for network configuration parameters that the DHCP server can pass to clients. If you have DHCP clients that are not Solaris clients, refer to the documentation for those clients for information about adding new options or symbols. Options are called symbols in the DHCP literature.

The dhtadm command and man page also refer to options as symbols. The following task map lists tasks you must perform to create, modify, and delete DHCP options and the procedures needed to carry them out. Before you create options, you should be familiar with the option properties listed in the following table. Vendor — Options specific to a client's vendor platform, either hardware or software.

The code is a unique number you assign to an option. The same code cannot be used for any other option within its option category. The code must be appropriate for the option category:.

Associated Data

The data type specifies what kind of data can be assigned as a value for the option. Valid data types are:. The presence of the option indicates a condition is true, while the absence of the option indicates false. For example, the Hostname option which is a Standard option and cannot be modified is a Boolean. If it is included in a macro, it tells the DHCP server that it should consult name services to see if there is a host name associated with the assigned address.

For example, a client ID uses the octet data type. An initial U or S indicates whether the number is unsigned or signed, and the digits at the end indicates the amount of bits in the number. For example, a data type of IP and a granularity of 2 would mean that the option value must contain two IP addresses. The maximum number of values that can be specified for the option. Building on the previous example, a maximum of 2, with a granularity of 2 and a data type of IP Address would mean that the option value could contain a maximum of two pairs of IP addresses.

This option is available only when the option category is Vendor. It identifies the client class es with which the Vendor option is associated. This type of option makes it possible to define configuration parameters that are passed to all clients of the same class, and only clients of that class. You can specify multiple client classes. Only those DHCP clients with a client class value that matches one you specify will receive the options scoped by that class.

The client class is determined by the vendor of the DHCP client. For Solaris clients, the Vendor client class can be obtained by typing uname -i on the client. To specify the Vendor client class, substitute periods for any commas in the string returned by the uname command. If you need to pass client information for which there is not already an existing option in the DHCP protocol, you can create an option. Refer to Table 4—9 for information about each setting. See Table 4—9 for information about how to determine the vendor client class.

See Table 4—9 for information about the properties. For example, SUNW. Ultra-1 SUNWi86pc. Note that you must specify all of the DHCP option properties with the -d switch, not just the properties you want to change. You can use DHCP to install the Solaris operating environment on certain client systems on your network. Only Sun Enterprise Ultra systems and Intel systems that meet the hardware requirements for running the Solaris operating environment can use this feature. The following task map shows the high-level tasks that must be performed to enable clients to obtain installation parameters using DHCP.

Set up a Solaris server to support clients that want to install the Solaris operating environment from the network. This information can be used when you create the options and macros needed to pass network installation information to clients. To support clients that require Solaris installation from the network, you must create Vendor category options to pass information that is needed to correctly install the Solaris operating environment.

The following table shows the options you must create and the properties needed to create them. Vendor client classes listed here are suggestions only.

Fundamentals

You should specify client classes that indicate the actual clients in your network that need to install from the network. See Table 4—9 for information about how to determine a client's vendor client class. When you have created the options, you can create macros that include those options. The following table lists suggested macros you can create to support Solaris installation for clients.

BootSrvA option could be added to existing network address macros. The value of BootSrvA should indicate the tftboot server. These names are examples of clients you might have on your network. See Table 4—9 for information about determining a client's vendor client class. If you use dhtadm , it is better to create the options and macros by writing a script that uses the dhtadm command repeatedly. The following section, Writing a Script That Uses dhtadm to Create Options and Macros , shows a sample script that uses the dhtadm command.

You can create a Korn shell script by adapting the example in Example 4—1 to create all the options listed in Table 4—11 and some useful macros. Be sure to change all IP addresses and values contained in quotes to the correct IP addresses, server names, and paths for your network. Load the Solaris vendor specific options. We'll start out supporting the Ultra-1, Ultra, and i86 platforms. Changing -A to -M would replace the current values, rather than add them.

Ultra-1 SUNW. Ultra SUNW. Includes Solaris and sparc macros. All clients identifying themselves as members of this class will see these parameters in the macro called SUNW. Ultra-1" class. By default, we boot these machines in 32bit mode. All clients identifying themselves as members of this class will see these parameters. Ultra" class. By default, we will boot these machines in 64bit mode. Our boot server happens to be the same machine running our DHCP server. Override the root settings which at the network scope setup for Install with our client's root directory. As superuser, execute dhtadm in batch mode and specify the name of the script to add the options and macros to your dhcptab.

For example, if your script is named netinstalloptions , type the command:. See Figure 4—17 and Figure 4—16 for illustrations of the dialog boxes you use to create options and macros. Use Table 4—11 to look up the option names and values for options you must create. Notice that the vendor client classes are only suggested values.

You should create classes to indicate the actual client types that need to obtain Solaris installation parameters from the DHCP service. The values for code, data type, granularity, and maximum are most likely to need modification. See Table 4—11 for the values. You can now create macros to pass the options to network installation clients, as explained in the following procedure.

See Table 4—12 for macro names you might use. To include another macro, type Include as the option name and type the macro name as the option value. The Solaris DHCP service can support Solaris client systems that mount their operating system files remotely from another machine, called the OS server.

Such clients are often called diskless clients. They can be thought of as persistent remote boot clients in that each time they boot, they must obtain the name and IP address of the server that hosts their operating system files, and then boot remotely from those files.

Production possibilities curve

Each diskless client has its own root partition on the OS server, which is shared to the client host name. This means that the DHCP server must always return the same IP address to the client, and that address must remain mapped to the same host name in the name service such as DNS. To accomplish this, each diskless client must be assigned a consistent IP address. In addition to the IP address and host name, the DHCP server can supply a diskless client with all the information needed to locate its operating system files on the OS server. However, you must create options and macros that can be used to pass the information in a DHCP message packet.

The following task map lists the tasks required to support diskless clients or any other persistent remote boot clients, and includes links to procedures to help you carry them out. Note that if you already created the options for network install clients, you need only create macros for the Vendor client types of the diskless clients. Use the smdiskless command to add operating system support on the OS server for each client.

Specify the IP addresses you reserved for each client. There are several ways to accomplish this, such as using the nisclient script or the nisaddcred command. For DHCP clients, you cannot use these methods because they depend on a static host name to create and store the credentials. The following procedure shows you how to create identical credentials for all DHCP host names. This procedure only produces credentials for the workstation, which apply only to the superuser logged in to the workstation. View the contents of the temporary file so you can copy the credentials and use them to create credentials for DHCP clients.

Most of this chapter describing the development and testing of the modeling tools is taken from Bojanowski et al. From a computational mechanics point of view, the analysis of riprap stability can be considered an FSI problem. FSI problems involve solving for the fluid flow forces on a solid surface, the response of that solid to the load, and subsequently, the change of the flow conditions caused by displacement of the solid. CFD software is used for solving fluid flows and CSM software is used for solving the deformations and stresses in solid bodies.

Historically, these software tools developed independently. Integrated FSI software, if available, is not yet mature nor well tested by industry. Until industry-proven FSI solvers are available, coupling highly robust and reliable CFD and CSM software through the development of data exchange and concurrent control coupling procedures appears to be the best approach for solving complex engineering FSI problems. For this project, TRACC developed coupling procedures between these software packages to support detailed analysis of riprap stability.

NCHRP report lists four major failure Modes for riprap revetments: 1 slope failure resulting in a slide, 2 riprap particle erosion, 3 erosion beneath the riprap armoring layer, and 4 erosion of the toe or key of the revetment leading to a slide. However, a model capable of describing scour beneath riprap revetment would be required to analyze failure Mode 3.

Modeling rock motion must overcome several challenges. One is sufficient characterization of the complex geometry of the bed in the vicinity of a pier or abutment. A riprap apron may include hundreds of rocks placed in a semi-organized manner in several layers. Representing each rock in the model is currently infeasible. However, sufficient engineering accuracy may be obtained with a reasonable approximation of the armored bed geometry. A second problem pertains to the extent of the domain to be modeled with CFD for proper representation of flood conditions. The upstream boundary of the computational domain needs to be a sufficient distance away from the zone of interest so that the velocity profile can develop by the time the flow reaches the area of the bridge.

Variations in river bed bathymetry constantly perturb the velocity profile. In most cases, placing the upstream boundary at least ten river hydraulic diameters upstream is sufficient. Similarly, the downstream outlet boundary must be sufficiently removed from flow obstructions so that recirculation zones created by flow obstructions, such as bridge piers, do not cross the outflow boundary. If the downstream boundary is too close to an obstruction, a recirculation zone may pull fluid into the domain through the outlet boundary violating the boundary conditions and the computation normally diverges.

The outlet boundary should also be sufficiently removed from the zone of interest. Placing the outflow boundary at least ten river hydraulic diameters downstream of the last obstruction is usually sufficient. However, physically obtaining detailed bathymetry of a river bed is difficult and expensive. Proper handling of the changes in the geometry within the CFD model is a third issue. These capabilities allow for the deformation of the computational mesh to accommodate moving boundaries.

During this process, new cells are not created and the solution is mapped from the old mesh to the new deformed mesh. However, large displacements of rocks as well as collisions between the rocks may cause the stretched cells to lose sufficient cell quality for an accurate solution of the governing equations or the algorithm may collapse cells causing negative volume cell termination of the computation. LS-DYNA software is a general purpose finite element program capable of simulating highly non-linear problems in structural mechanics including changing boundary conditions such as contact forces between rocks that change over time , large displacements, large deformations, and non-linear material property relations.

LS-DYNA includes morphing and automatic remeshing interaction; however, the coupled CFD solver is not capable of handling the large domains required for stream flood modeling. Therefore, the primary objectives of numerical modeling tool development for this project were as follows:. After development of the tools, they were tested by application to a case study of riprap at a bridge pier in the Middle Fork Feather River described in chapter 5. The following section describes validation of the methodology. The coupled FSI modeling tools were validated against the physical modeling described in chapter 3.

After validating the numerical modeling tools against the flume modeling data, the results of the physical experiments were scaled up using Reynolds number similarity to evaluate the modeling with full-scale geometry. The numerical model geometry was derived from scaling up the experimental flume setup by a factor of Figure 13 shows the plan view of the domain prototype dimensions including the rectangular channel, abutments forming the contracted section, and the riprap aprons intended to protect against local abutment scour. In the numerical analysis, only a half of this symmetrical domain was modeled to reduce the computational burden.

The DHCP Manager Window

Figure 14 shows the domain in a cross-section view. Plan view prototype domain. Cross-section view of the prototype domain. One challenge for the numerical model was to determine the appropriate level of detail for the description of the rocks in the riprap apron, including randomized size, shape, and placement. To address this challenge, a limited number of rocks were allowed to move with the majority being fixed in the modeling. This process cannot be automated and is very time consuming. Also, the structural part of the coupling relies on simulation restart capabilities in LS-DYNA that consume a significant amount of computer memory and time.

The more movable rocks there are in the model, the longer it takes to restart the LS-DYNA model in each coupling time step. This is one of the limits of the coupling mechanism. These coupling limits, along with the domain remeshing in CFD, are the most time consuming elements of the computation. For these reasons, the number of movable rocks was limited to The fine mesh following all feature curves on the rocks were retained only for the movable rocks. The mesh in the CFD model around the movable rocks is very dense but coarsens farther away from them. Approximately 3, stationary rocks were manually placed in the testing area.

Their packing was not as dense and random as in reality because of computational limitations. After placing the rocks, the domain was wrapped with the surface wrapper before building the volume mesh. For statistical purposes, correlation coefficients measured at the same number of separating loops but at different times have been averaged. Even after 11 loops, RPM is as high as after one cycle [ 39 ].

The observed persistence of MDM with field cycling is consistent with predictions for exchange-bias induced magnetic memory. Indeed, in these systems, the magnetic domain template imprinted in the AF layer is frozen, meaning it does not change while the magnetic field is cycled, as long as the temperature is kept constant below the blocking point. The domain pattern in the F layer will therefore tend to always retrieve that same unchanged magnetic template, independently from the number of field cycles [ 45 ]. Persistence of MDM through field cycling.

The MDM results previously discussed in this chapter were obtained by cross-correlating entire speckle patterns altogether. The associated correlation numbers provided an ensemble average microscopic information, but no spatial dependency was probed. Spatial information is however included in the 2D speckle patterns which are being correlated for the estimation of MDM. This spatial information can be exploited to extract information about possible spatial dependency in MDM. Each 2D speckle pattern, such as the one in Figure 7 , represents the intensity of the x-rays coherently scattered by the material.

Because the scattering process involves an inversion from the real space to the scattering space, the spatial scale on the speckle images is an inverse of a distance. A common quantity to locate positions in the speckle patterns is the scattering vector q. The origin of the vector q is the center of the scattering pattern, as illustrated in Figure 9. The magnitude of q indicates spatial scales d being probed in the real space. The larger q is, the smaller the features in the real space.

Most scattering patterns observed when probing magnetic domain patterns in PMA films show a ring. The presence of the ring reveals a magnetic periodicity in the domain pattern with an isotropic arrangement no preferred direction. This magnetic period is basically twice the domain width, as one period include a pair of up and down domains. By cross-correlating selected regions of the scattering speckle pattern rather than the entire pattern, one obtains spatially dependent correlation numbers.

This is useful to detect any spatial correlation features occurring at the nanoscale. To study the spatial behavior of MDM, in particular its dependence on q , cross-correlation is performed on selected rings of the speckle patterns.

Ageism: The Relationship between Age Stereotypes and Age Discrimination | SpringerLink

The rings are concentric, centered about the origin of the scattering pattern. Because speckle patterns are collected at specific points in field H along the magnetization loop, the exploration of spatial dependence in MDM may be done at each field value H. The films were ZFC below the blocking temperature. Speckle patterns were collected at low temperature, throughout the magnetization cycle and several subsequent loops.

Ring selective cross-correlations were carried out. The presence of these satellite peaks suggested a spatial superstructure in MDM. Topographical AFM images of the surface of the films indicated that D nearly matched the average distance between structural defects in the material. Since the speckle patterns used for the evaluation of MDM are 2D images, one can explore the spatial dependence of MDM in at least two directions.

These observations suggested the existence of some hidden rotational symmetries in the formation of the disordered magnetic domain patterns in these films. The results discussed in the previous sections show the occurrence of MDM via exchange bias when the film is cooled down to low temperatures, well below the blocking temperature T B. For each point, the temperature was finely controlled and stabilized via a cryogenic environment. The resulting correlation maps are shown in Figure The correlation maps in Figure 18a show the occurrence of high MDM extending throughout a wide region of the magnetization loop at all temperatures below TB.

At all temperatures below T B , MDM reached a high value plateauing over a large region of field values around the coercive point. The temperature dependence of MDM may be compared to the temperature dependence of the magnetization loop. The shape of the magnetization loop in the ZFC state, as seen in Figure 18b is symmetrical, centered about the origin.

The loop has an hourglass-like shape; it is narrow at the center and opens up at the extremities, due to the presence of exchange couplings. When increasing the temperature from the ZFC state, the overall shape of the magnetization loop remains the same, but the magnitude of the opening, or hysteresis, progressively decreases.

Despite the changes observed in the magnetization loop while warming the film up from the ZFC state, MDM remains strong and extended at all temperatures below T B. Slices through the correlation maps, shown in Figure 18c , all show the same trend: low correlation at nucleation, sharply increasing to reach a high correlation plateau in the central region of the magnetization loop, and then sharply decreasing toward saturation.

At that stage, the correlation map shows nearly zero correlation, becoming all blue. Above TB, these exchange couplings disappear. Consequently, the magnetic domain template which was imprinted in the AF layer throughout the uncompensated spins at the interface is lost once the magnetic field is cycled again. In the absence of magnetic template, and since the film is smooth absence of defects , the magnetic domains in the F layer nucleate and propagate randomly.

Next question is what happens if the film is now field-cooled FC , i. The resulting correlation maps showed drastic changes as a function of the magnitude of the cooling field [ 33 ]. The result of this study is summarized in Figure This high MDM extends from nucleation lower left corner of the correlation map all the way up to saturation upper right corner of the correlation map.

When HFC is increased up to moderately high values, high MDM is still observed, with a wide correlation plateau extending throughout a large range of field values from nucleation to saturation. The imprinted domain pattern constitutes a template for the domain reversal in the F layer. Because of exchange couplings occurring between the Co spins in the F layer and the uncompensated interfacial Mn spins in the AF layer, the domains form in a way to match the underlying template. The matching persists at higher field values, all the way up to near saturation. This is possible because, even though the magnetic domains of opposite magnetization expand and shrink, the specific topology of the domain pattern still matches the underlying template, as illustrated in Figure The imprinted pattern in the AF IrMn layer is shown in green color, the domain pattern in the F layer is shown in orange color.

Arrows indicate magnetization direction. In the FC states, the magnetic domain template imprinted in the film has an unbalance of up and down domains, and the net magnetization is non-zero. However, if the magnitude HFC of the cooling field remains in a certain range above Hcr , the imprinted pattern, still formed of interlaced up and down domains, provides a template that entirely drives the reversal of the magnetic domains in the F layer.

The topology of the imprinted pattern in the FC state resembles that of the imprinted pattern in the ZFC state. High MDM is therefore maintained throughout the entire magnetization process. If the magnitude HFC of the cooling field approaches saturation value Hs , the imprinted magnetic domain pattern does not include long interlaced magnetic domains of opposite magnetization anymore but a few bubble domains sparsely scattered throughout the film.

This imprinted template is not able to drive the magnetic domain formation throughout the entire reversal but only at the extremities, that are the nucleation and the saturation points, as illustrated in Figure These results demonstrate the possibility to induce and control nanoscale MDM in exchange biased films by adjusting the field cooling conditions. However, MDM can be almost eliminated, by cooling the material under high magnetic field, approaching saturation and higher. Magnetic domain memory MDM is an unusual property exhibited by certain ferromagnetic films, where the microscopic magnetic domains tend to reproduce the same topological pattern after it has been erased by an external magnetic field.

In most ferromagnetic materials, MDM does not occur.

Ring Theory - Concept of Integral domain and Skew Field(Division Ring) in hindi

When an external magnetic field is applied and cycled, microscopic magnetic domains form and propagate throughout the material in non-deterministic ways. However, it has been found that some ferromagnetic thin films with perpendicular magnetic anisotropy PMA do show significant MDM under certain structural and magnetic conditions.

One structural condition is the presence of defects. This disorder-induced MDM is caused by the presence of microscopic structural defects, playing the role of pinning sites for the domain nucleation. When the material is cooled down below its blocking temperature, a specific magnetic domain pattern gets imprinted into the AF layer. When the field is cycled at low temperature, the frozen imprinted AF pattern then plays the role of a template for the domain formation in the F layer.

The resulting high MDM extends throughout a wide range of field values, from the coercive point to nearly saturation. Additionally, it was found that the amount of EC-induced MDM can be varied by adjusting the magnitude of the field applied during the cooling. If, however, the material is cooled under a nearly saturating field, MDM vanishes, except at the nucleation and saturation extremities of the magnetization cycle. A particular question is if there are other ways to induce and control MDM in a material. If the material is illuminated by too intense x-rays, the film may lose its EC properties and MDM may vanish.

This finding, which resonates with the emergent all-optical magnetic switching phenomena observations [ 48 , 49 , 50 ], suggest that EC-induced MDM could be controlled by light illumination. Ultimately, the ability to induce and control MDM in PMA ferromagnetic film, either by structural disorder, or by exchange couplings and light illumination, may offer a tremendous potential for improving technological applications in the field of magnetic recording and spintronics.

Help us write another book on this subject and reach those readers. Login to your personal dashboard for more detailed statistics on your publications. Edited by Neeraj Panwar. By Abdel-Baset M. We are IntechOpen, the world's leading publisher of Open Access books.


  1. The key to Bedroom Satisfaction?
  2. Chapter 4 Administering DHCP (Solaris DHCP Administration Guide).
  3. Neuroproteomics (Frontiers in Neuroscience).

Built by scientists, for scientists. Our readership spans scientists, professors, researchers, librarians, and students, as well as business professionals. Downloaded: Abstract Magnetic domain memory MDM is the ability exhibited by certain magnetic materials to reproduce the exact same nanoscale magnetic domain pattern, even after it has been completely erased by an external magnetic field. Keywords magnetic domains ferromagnetic films perpendicular magnetic anisotropy magnetic domain memory defect-induced memory exchange-coupling induced memory.

Introduction to the principles of MDM 1. Magnetic domain patterns in ferromagnetic films Ferromagnetic materials are typically composed of magnetic domains. The case of thin films with perpendicular magnetic anisotropy Thin ferromagnetic films with perpendicular magnetic anisotropy PMA [ 16 ] exhibit a particularly rich set of magnetic domain patterns. Magnetic domain memory Magnetic domain memory MDM is the tendency for magnetic domains to retrieve the same exact same pattern after the pattern has been erased by a saturating magnetic field.