反強磁性層内疎結合模型を用いた補償・非補償配置によらない交換磁気異方性発現機構

概要

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Since the discovery, unidirectional anisotropy appeared in an exchange coupled ferromagnetic(F)/antiferromagnetic (AF) layers has been applying to pinning for ferromagnetic layers of various spin devices. However, the fundamental understanding is not obtained still clearly. Authors have already demonstrated a mechanism of unidirectional anisotropy appearance for compensated AF-interface on the simple cubic (sc) lattice. The mechanism has been obtained by just assuming a loosely coupled layer in the AF region, without giving any restriction to the classical Heisenberg spins, with perfect interfaces. Similar mechanism has been also employed in uncompensated AF-interfaces. The difference from compensated one was only the F/AF coupling form (spin flop or collinear) interaction, unidirectional anisotropy did not depend on compensated or uncompensated, and appeared with the loose coupling in the AF region. The origin of the unidirectional anisotropy energy does not come from the F/AF interfaces but from the inner AF coupling defects. As reported previously, a large decrease of AF-interaction from 1/10 to 1/1000 of usual AF-interaction was necessary to obtain the unidirectional anisotropy in the systems. The defect mode will have to be analyzed in the future. One of the other issues is calculation size dependency in the fcc systems.
2009-04-01