Grain-size dependent demagnetizing factors in permanent magnets S. Bance, 1, a) B. Seebacher, 1 T. Schrefl, 2 L. Exl, 3 M. Winklhofer, 4, 5 G. Hrkac, 6 G. Zimanyi, 7 T. Shoji, 8 M. Yano, 8 N. Sakuma, 8 M. Ito, 8 A. Kato, 8 and A. Manabe 8 1) Department of Technology, St P¨ olten University of Applied Sciences, Matthias Corvinus-Str. 15, 3100 St P¨ olten, Austria 2) Center for Integrated Sensor Systems, Danube University Krems, 2700 Wiener Neustadt, Austria 3) Solid State Physics, Vienna University of Technology, 1040 Vienna, Austria 4) Department of Earth and Environmental Science, Ludwig-Maximilians-Universit¨ at M¨ unchen, 80333 Munich, Germany 5) Fakult¨ at f¨ ur Physik, Universit¨ at Duisburg-Essen, 47048 Duisburg, Germany 6) CEMPS, Harrison Building, University of Exeter, Exeter, EX4 4QF, UK 7) Department of Physics and Astronomy, UC Davis, One Shields Avenue, Davis, California 95616, USA 8) Toyota Motor Corp., Toyota City, 471-8572, Japan (Dated: 2 April 2015) The coercive field of permanent magnets decreases with increasing grain size. The grain size dependence of coercivity is explained by a size dependent demagnetiz- ing factor. In Dy free Nd 2 Fe 14 B magnets the size dependent demagnetizing factor ranges from 0.2 for a grain size of 55 nm to 1.22 for a grain size of 8300 nm. The comparison of experimental data with micromagnetic simulations suggests that the grain size dependence of the coercive field in hard magnets is due to the non-uniform magnetostatic field in polyhedral grains. PACS numbers: 75.60.Ch, 96.12.Hg, 75.60.Ej a) simon.bance@fhstp.ac.at; http://academic.bancey.com; Copyright 2014 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Bance et al., “Grain-Size Dependent Demagnetizing Factors in Permanent Magnets.“ J. App. Phys. vol. 116 no. 23 pp. 233903 and 1