ホイスラー合金層を用いた多結晶面直電流型巨大磁気抵抗素子の高出力化

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For the topic of CPP-MR, we have developed a Mg-Ti-O (MTO)-based tri-layer spacer and obtained large MR output in CPP-MR devices using it. Specifically, with a tri-layer spacer of Ag/MTO/Ag, large delta-Vmax over 10 mV is obtained (highest of 16 mV) in our CPP-MR devices with RA of 200-300 mΩ μm2. We find that the large MR output is very likely to originate from the formation of metallic Ag channels penetrating the MTO layer.For the topic of spin current generation, we have studied the spin Hall magnetoresistance (SMR) in non-magnetic/ferromagnetic (NM/FM) bilayer with novel conductive NM layer. As a result, considerable SMR ratio has been observed in such a bilayer stack, which is comparable to the SMR magnitude observed in stacks with NM being a noble metal such as Pt. The origin of such a SMR can be related to the large spin-orbit coupling in the NM layer or the Rashba-Edelstein effect at the NM/FM interfaces. On the other hand, we have studied the SMR in NM1/FM/NM2 tri-layer stack to investigate how a second interface affects the overall spin-orbit torques (SOTs) in such a system. As a result, we have found that the SOTs are strongly related to the spin diffusion length of FM layer and NM2 layer placed upon it, and specifically, related to the spin transport transparency at the FM/NM2 interfaces. By calculating the respective effective spin mixing conductance of the systems, we quantitatively evaluate the damping-like and field-like SOTs in such a system, providing useful information to the control of SOTs at NM/FM interfaces.