Cellular magnetic domains in Fe–Ga alloys

Abstract

A peculiar magnetic domain pattern (so-called cellular domain structure) was recently observed in Fe–Ga alloys, which was claimed to be responsible for desirable hysteresis-free and isotropic magnetization behaviors and to be associated with the reported non-Joulian magnetism [H. D. Chopra and M. Wuttig, Nature 521, 340 (2015)]. So far, such cellular domain phenomenon is observed only in Fe–Ga single crystal specimens of thin disk shape and with special thermal history. In this Letter, we report that the cellular domain structure is also observed in as-cast polycrystalline Fe–Ga alloys that are simply synthesized by arc-melting without special thermal treatment. For comparison, the cellular domains observed in an Fe–Ga single crystal specimen of rectangular prism shape are also presented. The cellular domain structure is discussed in light of a surface domain phenomenon and is found to be well interpreted by the Stephan model [Von W. Stephan, Exp. Tech. Phys. 4, 153 (1956)] based on classical domain theory, contrary to the Chopra–Wuttig model relying on the hypothesized charge density wave theory.