Nonlinear conjugate gradient methods in micromagnetics
J. Fischbacher,
Alexander Kovacs,
Harald Oezelt,
T. Schrefl,
L. Exl,
J. Fidler,
D. Suess,
N. Sakuma,
M. Yano,
A. Kato,
T. Shoji,
A. Manabe
Affiliations
J. Fischbacher
Center for Integrated Sensor Systems, Danube University Krems, 2700 Wiener Neustadt, Austria
Alexander Kovacs
Center for Integrated Sensor Systems, Danube University Krems, 2700 Wiener Neustadt, Austria
Harald Oezelt
Center for Integrated Sensor Systems, Danube University Krems, 2700 Wiener Neustadt, Austria
T. Schrefl
Center for Integrated Sensor Systems, Danube University Krems, 2700 Wiener Neustadt, Austria
L. Exl
Faculty of Mathematics, University of Vienna, Vienna, 1090 Wien, Austria
J. Fidler
Institute for Solid State Physics, TU Wien, 1040 Wien, Austria
D. Suess
CD-Laboratory for Advanced Magnetic Sensing and Materials, TU Wien, 1040 Vienna, Austria
N. Sakuma
Toyota Motor Corporation, 1200 Mishuku, Susono, Shizuoka 410-1193, Japan
M. Yano
Toyota Motor Corporation, 1200 Mishuku, Susono, Shizuoka 410-1193, Japan
A. Kato
Toyota Motor Corporation, 1200 Mishuku, Susono, Shizuoka 410-1193, Japan
T. Shoji
Toyota Motor Corporation, 1200 Mishuku, Susono, Shizuoka 410-1193, Japan
A. Manabe
Technology Research Association of Magnetic Materials for High-efficiency Motors (Mag-HEM) Higashifuji-Branch, 1200 Mishuku, Susono, Shizuoka 410-1193, Japan
Conjugate gradient methods for energy minimization in micromagnetics are compared. The comparison of analytic results with numerical simulation shows that standard conjugate gradient method may fail to produce correct results. A method that restricts the step length in the line search is introduced, in order to avoid this problem. When the step length in the line search is controlled, conjugate gradient techniques are a fast and reliable way to compute the hysteresis properties of permanent magnets. The method is applied to investigate demagnetizing effects in NdFe12 based permanent magnets. The reduction of the coercive field by demagnetizing effects is μ0ΔH = 1.4 T at 450 K.
