Effect of a Randomly Oriented Cubic Crystalline Anisotropy on Stoner-Wohlfarth Magnetic Hysteresis Loops

Experimental hysteresis loops are presented for thin anisotropic films (81% nickel-19% iron) in which cusplike bumps exist for angles larger than 20° between the applied field and the hard magnetic direction. The Stoner—Wohlfarth model for a uniaxially anisotropic magnetic material indicates these cusps should vanish for angles larger than 13°, and a new model is developed which accounts for the larger angles which are observed. This new model takes into account, in an approximate way, the effects of the crystalline anisotropy in randomly oriented, polycrystalline magnetic materials. In addition to providing an understanding of the observed hysteresis loop behavior, this model leads to the suggestion of a possible mechanism for creep in magnetic thin-film memory devices. According to this suggestion, creep may be reduced by reducing the magnitude of the crystalline anisotropy of the magnetic material, and a discussion of some possible alloys for accomplishing this goal is given.