Exchange Bias in Ni-Mn-Sn Heusler Alloy Films

Abstract

We report a relatively large exchange bias eect observed for the rst time in NiMnSn thin lms with dierent microstructure and composition: a Ni50Mn36Sn14 epitaxial lm (A), a Ni50Mn43Sn7 lm which is phase decomposed (B), and a NiMn/Ni50Mn25Sn25 bilayer (C).Despite the samples dier markedly in both microstructure and composition HEB does not substantially diers at 5 K. Exchange bias decreases with increasing T approximately as HEB(T ) ∝ HEB(5 K)/T with HEB(5 K) of 180 Oe and 60 Oe for sample B and C, respectively and almost linearly for sample A with HEB(5 K) = 65 Oe.Blocking temperature where the exchange bias vanishes is 40, 50 and 80 K for sample A, C and B, respectively.The results suggest that the role of AFM/FM interfaces is not substantial in formation of exchange bias in NiMnSn Heusler alloy lms and exchange bias is rather related to AFM/FM interactions in nanoscale.