muMAG MICROMAGNETICS WORKSHOP Wednesday, November 8, 1995
Philadelphia, PA.

Larry Bennett (NIST) announced a forthcoming micromagnetic workshop at the George Washington University in May, 1996. He asked those present to watch out for future announcements about the workshop, and to endeavor to actively participate in it. For more information about this workshop, and to get on the mailing list, send e-mail to imr@seas.gwu.edu.

II. Klaus Ramstöck (University of Erlangen-Nürnberg) presented work on the computation of domain walls in a uniaxial medium of infinite extent. He proposed using this problem as a benchmark for measuring algorithm performance by utilizing different techniques in solving it. This may permit isolating the influence of solution methods on the calculated results and computational speed.

III. Jimmy Zhu (University of Minnesota) presented simulated magnetic structures in rectangular and circular sub-micron thin metallic film samples. These results were compared with experimental data.

IV. Jim Blue (NIST) presented an update on the muMAG Public Portable Code Project. He described key organizational and implementation issues pertaining to problem domain definition, portability, applicable algorithms, software engineering design issues, software package development, distribution and support issues.

V. The following speakers presented solutions of the First Standard Problem. This problem requires the calculation of magnetization curves and magnetization structures of a 1 x 2 micron permalloy film. The complete specification of the problem can be found at internet web page http://www.ctcms.nist.gov/~rdm/stdprob_1.html.

• John Oti (NIST). Simulation results presented: Final zero field magnetization structures beginning with uniform and random initial magnetization states, and magnetization structures and curves resulting from application of longitudinal and transverse magnetic fields, beginning with uniform and random initial magnetization states.
• Jay Hoinville (Maxtor). Simulation results presented: Final zero field magnetization structures beginning with circularly oriented and canted uniform initial magnetization states; magnetization structures and curves as functions of applied longitudinal and transverse magnetic fields; low field susceptibility curves. These results may not be a valid solution to the standard problem, as Jay has noted an error in his handling of the exchange stiffness parameter.
• Mike Donahue (NIST). Simulation results presented: Magnetization structures and hysteresis loops for applied longitudinal and transverse magnetic fields, and zero field structures for a variety of initial conditions, including random moments, uniform magnetization, four-domain, vortex, and seven domain states.

VI. The following points were made during the general discussion part of the workshop:

Standard Problems

1. Standard problems should be simple, and solutions should contain detailed specification of input parameters and solution methods. The problem sizes should be sufficiently small to run reasonably fast on personal computers. Solutions to standard problems should be posted on the internet in an agreed upon format. Also it would be helpful to have individual energy components (e.g., exchange, demag and anisotropy) plotted as a function of iteration count.
2. First Standard Problem should be made more specific with respect to mesh size and parameters of dynamic equations and additional solutions tried.
3. Proposal described above in part II of these minutes should be adopted as a standard problem. There is indication that other workers are involved in this kind of modeling.
4. Experimental data should be made available to verify solutions of standard problems. Larry Bennett informed that Lakeshore Corp. has offered to provide experimental permalloy samples to be used in verifying the First Standard Problem.

General Comments

Anybody interested in using standard problems is invited and encouraged to participate in the problem development process. The more participation, the better the results.