CPP-GMR pseudo spin-valves using ferromagnetic Heusler layer Co_2Fe(Ga_(0.5)Ge_(0.5)) and nonmagnetic Heusler spacer Cu_2CrAl

摘要

The current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices utilizing Co-based full Heusler alloys in the past few years have drawn much attention due to their potential application in the read sensors of ultrahigh density hard disk drives. Recent studies by Li et al and Sakuraba et al have demonstrated large MR ratio of over 50% and resistance change-area (ΔRA) product of ～12 mΩ μm~2 by depositing epitaxial CPP-GMR film stacks on MgO (001) single-crystalline substrates. In these works, Ag was adopted as the spacer layer. On the other hand, other spacer materials have been proposed theoretically and experimentally. Nikolaev et al realized the all-Heusler CPP-GMR devices with ferromagnetic Co_2MnGe (CMG) and nonmagnetic Rh_2CuSn (RCS) Heusler films. Desirable band matching for the majority spins of CMG and RCS was proved by band calculations and finally the ΔRA of 4 mΩ μm~2 was achieved. Another work by Ko et al demonstrated the possible usage of Heusler spacer Cu_2CrAl (CCA) for the CPP-GMR devices, yet no experimental work was done. In this work we investigated the CPP-GMR properties of pseudo spin-valves using ferromagnetic Heusler layer Co_2Fe(Ga_(0.5)Ge_(0.5)) (CFGG) and nonmagnetic Heusler spacer CCA.