Mag-O-Mat tutorial -> Setting Anisotropy Properties Manually

In this topic you will learn how to manually specify anisotropy properties for a sample. A detailed discussion of media magnetic-anisotropy properties are given in MagOasis software product manuals. Any number of uniaxial and pinning anisotropies of different types can be defined for each cell of a sample. Each type of anisotropy is characterized by an easy axis, an anisotropy-field strength and a thermal coefficient.

You will continue to work with the Magsimus component you started with in the previous topic (Setting magnetization states manually). The preliminaries are already in place; all that remains to be done is for you to now ready Mag-O-Mat for anisotropy editing. To do so, first, make sure that the map plane U-V is selected in the Arrays layout tab, then click on the Material properties tab and select Anisotropy from the Characteristic box. The input area below this box will change to accept anisotropy inputs (Fig.12a). This area for now is disabled as Mag-O-Mat is currently not expecting any inputs (the map box should look like Fig. 12b). No anisotropies have been defined for the sample, so only the cell outlines of the sample is displayed. That will change as we add new anisotropies below. It is important to keep in mind that the only anisotropies displayed in Mag-O-Mat are those created using it or other Mag-O-Mat compatible tools. The anisotropies created by other means such as those that are available within the MagOasis applications are not yet visible in Mag-O-Mat (though this might change in the future).

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Fig. 12. Mag-O-Mat's Material properties tab (a) and the map box (b) at the beginning of Manual-mode setting of anisotropy properties.

Take these next steps to create your first anisotropy definition. Make sure the toggle button above the map area (labeled Click to Zoom or Click to edit) reads Click to Zoom and that the annotation next to it reads K Editing (you may have to click the button once to accomplish this). Use the mouse to sweep out a region of the map similar to Fig. 13 (the cells for this region will become drawn in green color, indicating that they are ready to be modified). The anisotropy input  area (within the Anisotropy frame)  are now enabled. Enter the following inputs: In the Theta frame enter Mean = 90 and Dev. = 0; in the Phi frame enter Mean = 90, Dev. = 0; in the Name box enter Uniaxial 1; select Uniaxial in the Anisotropy type list box and enter  10 in the K Field box. Select 2 in the Line thickness list box.

Fig. 13. Swept out Mag-O-Mat map-box region discussed in text.

The selection in the Anisotropy type box specifies that this will be a uniaxial-anisotropy definition. The input in the K Field box represents the anisotropy field strength while the inputs in the Theta and Phi frames represent the angular (orientation) coordinates of the anisotropy easy axes in the cells. The angular values are assigned randomly about the mean values, within bounds given by the specified angular deviations. The Name input specifies a unique name by which the anisotropy is identified by all MagOasis application software.  The defined anisotropies are numbered sequentially in the order they are created by Mag-O-Mat.  The drop-down list to the right of the Name box contains this numbering. Making a selection here fills the input area with values for the chosen anisotropy, which can then be subsequently modified further. An anisotropy selected in the list can be removed by clicking the Delete button; All anisotropy definitions are removed by clicking the Delete all button. The inputs entered using the Line thickness list box or Color button are not anisotropic properties; their roles are esthetic ones – you use them to specify the line thickness and color you want to draw the easy axes of the anisotropy definition with. Clicking the Color button displays a standard Windows™ Color dialog box for selecting a new line color. Unlike magnetization vectors, your anisotropy definitions will be displayed in Magsimus (or other MagOasis application software) with the same attributes they are displayed locally in Mag-O-Mat. The choice of line thickness is intended to make the anisotropy axes stand out from the magnetization vectors when displayed in Magsimus.

Click the Accept button to apply the new anisotropy to the map. The map box should now look like Fig. 14. The bi-arrows represent the easy axes of the uniaxial anisotropy we just defined for the group of cells.

Fig. 14. Uniaxial anisotropy defined manually in Mag-O-Mat's map box.

Next, you will define some pinning anisotropy. Sweep out a new map region that partially overlaps the old one as shown in Fig. 15a.  Select Pinning from the Anisotropy type box.  In the Phi frame enter Mean = -45, Dev. = 0, and then click the Accept button to apply the new definitions to the map box. The map box should now look like Fig. 15b. The pinning anisotropy axes are represented by normal arrows (much like magnetization vectors). Notice that both types of anisotropies are defined for the cells in the overlapped region. Also notice that the pinning anisotropy was drawn in a different color from the uniaxial anisotropy. Mag-O-Mat assigns the line colors randomly with each new anisotropy definition, but you can always change these to your taste as previously indicated. Finally, apply the new anisotropy definitions to your Magsimus session by clicking the Transfer button. Your displayed design in Magsimus should now look like Fig. 15c.

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Fig. 15.  Figures for manual-mode setting of anisotropy properties discussed in the text

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