Mossbauer effect study of correlation between structure and exchange-bias effect in ferromagnetic Fe/antiferromagnetic FeSn2 bilayers -: art. no. 063513

Antiferromagnetic (AF) FeSn2(001) epitaxial and polycrystalline layers were grown in ultrahigh vacuum under various conditions on clean InSb(001) substrates and covered by polycrystalline ferromagnetic Fe layers, forming a new system with exchange bias. Isotopically enriched Fe-57- and (FeSn2)-Fe-57-tracer layers were placed on either side of the Fe/FeSn2 interface for a microscopic investigation of the spin structure and atomic interdiffusion phenomena in near-interfacial regions by Fe-57 conversion electron Mossbauer spectroscopy (CEMS) at room temperature and T=10 K. Several spectral components, assigned to pure bcc Fe, Sn-containing bcc Fe, AF-ordered FeSn2, and paramagnetic FeSn2 were resolved in the CEM spectra. Evidence is provided for interdiffusion across the interface. The temperature dependence of the exchange-bias field H-E was measured by magnetometry. The CEMS data provide evidence for a correlation between H-E at low T and chemical disorder (defects) in the FeSn2 films via the intensity of the paramagnetic line. These results support the assumption that exchange bias is related to the presence of AF domains formed via magnetic defects in the antiferromagnet. The T dependence of H-E suggests interfacial exchange-coupling energies higher than the AF wall energy. (C) 2005 American Institute of Physics.