Oxs Extension Module:
CED_UniaxialAnisotropy
Description:
This is a generic Oxs extension object, derived from the Oxs_Energy
class. It provides uniaxial anisotropy with second (K1) and fourth
(K2) order terms. In the easy axis case (K1>0) the energy density E
is computed by
E = K_{1}u×m^{2}
+ K_{2}u×m^{4},
where m is the reduced (unit) magnetization and u is the
easy axis. Here the energy is zero if the magnetization is aligned
with the easy axis.
In hard axis case (K1<0) the energy is offset so that the zero point
occurs when the magnetization lies in the easy plane (i.e., orthogonal
to the hard axis). In this case the energy density is given by
E = K_{1}(u·m)^{2}
 K_{2}(u·m)^{4}.
Either way, the field H is computed via the relation
µ_{0}M_{s}H =
2K_{1}(u·m)u
+ 4K_{2}(u·m)^{3}u,
where M_{s} is the saturation magnetization.
This class was written and contributed by
Jürgen Zimmermann, Richard Boardman and Hans
Fangohr of the Computational Engineering and Design Group,
University of Southampton.
Installation:
Download the header and source code files below, and follow the general Oxs extension installation
instructions.
Usage:
MIF 2.x files written to use this class should include a Specify block
of the form

Specify CED_UniaxialAnisotropy:name {
 K1 k1_value
 K2 k2_value
 axis anisotropy_axis
 }
The values for the K1 and K2 parameters should be
scalar field objects, and axis should be a vector field
object. The only difference with respect to the stock
Oxs_UniaxialAnisotropy class is the inclusion of the K2 term.
Details:
 Authors: Jürgen Zimmermann, Richard Boardman, and Hans
Fangohr
 Affiliation: Computational Engineering and Design Group,
University of Southampton
 Oxs_Ext class: CED_UniaxialAnisotropy
 OOMMF releases: 1.2a3
 External libraries: none
 License: Public Domain
 Release date: 7July2004
Output from the three example MIF files, illustrating the effect of
increasing K2 relative to K1:
DISCLAIMER: This software was not
developed at and is not supported by the
National Institute of Standards and Technology. NIST assumes no
responsibility whatsoever for its use, and makes no guarantees,
expressed or implied, about its quality, reliability, or any other
characteristic.
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This page maintained by michael.donahue@nist.gov
27Nov2006