The origin of exchange biasing in FeMn͞Co bilayers is elucidated using magneto-optic Kerr effect and x-ray dichroism. It is found that the FeMn spin structure is aligned with the ferromagnetic (FM) moment of the Co layer, indicating that "spin flop" coupling is not the mechanism for exchange bias in this system. Futhermore, the Fe forms an uncompensated surface. It is likely that the FM Fe spins play a key role in the generation of the exchange bias. These results provide new insight to the mechanism of exchange biasing in metallic ferromagnetic͞antiferromagnetic systems.
The structural and magnetic properties of sputter deposited epitaxial Fe 7.5 A Pt tPt 001 multilayers tPt = 0-15 A are investigated using x-ray di raction, Kerr magnetometry, and x-ray magnetic circular dichroism XMCD. Xray di raction shows that there is a crystalline phase change from bct to fct at a Pt thickness of 4 A. The Fe XMCD is enhanced by 10 over its bulk value for Pt thickneses from 1-4 A bct region, and depressed relative to the bulk by 10-20 after transition to the fct phase. The Pt layers show a striking almost ferromagnetic" behavior. XMCD at the N2;3 edge shows that the Pt moment is nearly constant u p to tPt = 1 0 A, with a value of 0.5 B atom. Kerr magnetometry is used to determine the in plane magnetocrystalline anisotropy constant, K1, as a function of tPt. It is found that for the Fe thickness studied here, the easy axis switches from the bct 100 to the bct 110 direction with increasing tPt. This indicates that K1 has a zero crossing, which occurs at tPt 1:5 A. This strong variation in magnetic anisotropy is attributed mainly to the Fe Pt interface region. However, ferromagnetic Pt also contributes a signi cant v olume anisotropy which w e estimate at-82 10 6 erg cc.
Element-specific magnetic moments in Fe/V superlattices are studied using x-ray magnetic circular dichroism (XMCD). Superlattices are simultaneously deposited with the epitaxial orientations (100), (211), and (110), to explore the orientation dependence of these moments. The layer-averaged vanadium moments are antiparallel to those of the Fe and are larger than those observed in alloys with similar composition. The V moments decay monotonically and relatively slowly with distance from the Fe interface (exponential decay length: ) in qualitative agreement with recent calculations. In contrast to calculations, the magnitudes of the V moments fall on a universal curve for the three orientations.
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