Structure and transport properties of current-perpendicular-to-plane spin valves using Co2FeAl0.5Si0.5 and Co2MnSi Heusler alloy electrodes

We report the structure and transport properties of current-perpendicular-to-plane spin valves (CPP SVs) with Co2FeAl0.5Si0.5 (CFAS) or Co2MnSi (CMS) Heusler alloy magnetic layers and an Ag or Cu spacer layer. A multilayer stack of sub/Cr/Ag/Heusler/(Ag or Cu)/Heusler/Co75Fe25/Ir22Mn78/Ru was deposited on a MgO(001) single crystalline substrate by magnetron sputtering. Transmission electron microscopy observations showed epitaxial growth from the substrate to the top Heusler layer. The CPP SV with a CFAS/Ag/CFAS trilayer showed relatively large magnetoresistance (MR) ratios of 12% at room temperature and 31% at 12 K, with monotonous temperature dependence. However, the MR values of the SV with the CMS/Ag/CMS trilayer showed a different temperature dependence with a maximum value of 22% at 100 K. This might be related to the 90 degrees couplings between the two CMS layers. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3431530]