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Manuscript Title: Symmetric Neel walls in thin magnetic films.
Authors: A. Hubert
Program title: SYMMETRIC NEEL WALLS
Catalogue identifier: ACKB_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 1(1970)343
Programming language: Algol.
Computer: CDC 6600.
Operating system: CDC 6600 SCOPE 3.2.
RAM: 17K words
Word size: 60
Keywords: Solid state physics, Micromagnetism, Magnetic Thin films, Lorentz Microscopy, Domain walls, Neel walls, Ritz's method.
Classification: 7.7.

Revision history:
Type Tit le Reference
adaptation 0001 INTERNAL IMPROVEMENTS See below

Nature of problem:
In very thin magnetic films a domain wall type may occur which is characterized by the rotation of the magnetization direction in the plane of the film. The structure of these so-called Neel-walls depends essentially on four external parameters: the film thickness, the total wall rotation angle (connected with the value of the applied field) and two anisotropy constants characterizing the material. Both uniaxial and multiaxial anisotropy may thus be represented. The calculation of these walls yields the wall energies, the detailed wall structure, the characteristic wall widths in the core and the tail regions of the walls, and Aharoni's self-consistency parameter.

Solution method:
The walls are calculated by Ritz's method with a one-dimensional ansatz. This method has proved to give energies less than 1% higher than the exact result. The starting values of the variational procedure may be automatically computed by the program.

Restrictions:
The present program calculates only isolated walls in an infinite film. The investigation of interacting walls is being prepared. So far the results should only be applied to cases where walls are separated further than the external wall width calculated in the program. No net magnetic charge is allowed on the walls. The magnetic anisotropy must be a symmetric function of the magnetization component perpendicular to the wall and must be describable to sufficient accuracy by second and fourth order terms in this component.

Running time:
One wall needs between 20 sec and 60 sec on the TR4 and approximately one third of this time on the CDC 6600. The higher running times are needed if the second anisotropy constant does not vanish.

ADAPTATION SUMMARY
Manuscript Title: Symmetric Neel walls in thin magnetic films. An adaptation to increase the range of convergence.
Authors: A. Hubert
Program title: 0001 INTERNAL IMPROVEMENTS
Catalogue identifier: ACKB_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 1(1970)468
Programming language: Algol.
Classification: 7.7.

Nature of problem:
The adaptation consists of improvements to the internal organization to increase the range of convergence, particularly for high anisotropy ratios. Additional precautions have been introduced for the case of bad convergence. The output from the test run of this adaptation is essentially unaltered from that of the original program.