Temperature dependence of current-perpendicular-to-plane giant magnetoresistance in the junctions with interface tailored Heusler alloy electrodes

Current-perpendicular-to-plane, CPP, giant magnetoresistance, GMR junctions attract interests for application of sensor devices, such as read head element of hard disk drives. Temperature dependence of the CPP-GMR effects was investigated, in this study, for junctions consisting of the half-metallic Heusler alloy, Co₂(Fe-Mn)Si, electrodes and an L1₂-type Ag₃Mg spacer with the ultra-thin interface layers, Fe or Mg. For the Fe insert junctions, MR ratio exhibited local maximum at a temperature ranging from 50 K to 250 K which depends on the insertion thickness. The reason is unclear for the anomalous temperature dependence of the Fe junctions, however, a possibility is reduction of the Curie temperature for the Fe insert at the ultra-thin regime. On the other hand, MR ratios monotonically increased with decreasing the temperature for the Mg insert junctions, for which MR ratio of about 100% was observed at 10 K. Ratios of MR at 300 K to the low temperature are almost independent of the insertion thickness. Considering a fact that the shapes of MR curves nearly unchanged by the temperature change, it is suggested that the Mg insert works as a diffusion barrier at the Co₂(Fe-Mn)Si/Ag₃Mg interfaces.