09:30 〜 09:45
▼ [20a-W241-3] Large enhancement of magnetoresistance in thin NiAl-inserted Co2FeGa0.5Ge0.5/Ag/Co2FeGa0.5Ge0.5 CPP-GMR devices
キーワード：Band matched CPP-GMR
Current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices using Heusler alloy ferromagnetic (FM) layers have attracted much interest recently for potential applications as read sensors of future ultra-high density magnetic recording system above 2Tbit/in2 due to the low devices resistance. [1] However, In order to produce a sufficient signal-to-noise, further enhanced the magnetoresistance (MR) output i.e., resistance-change area product (ΔRA) are desired in CPP-GMR devices.
We have investigated the effect of the insertion of a thin NiAl layer (≤ 0.63 nm) to the Co2FeGa0.5Ge0.5(CFGG)/Ag interface on the MR properties in CFGG/Ag/CFGG devices. The Insertion layer of NiAl was selected because a good band structure matching between NiAl and Heusler compounds has been implied from the similar band dispersions along the <001> at k// = (0,0). [2,3] We also have clarified that the interfacial band matching at (001)-oriented NiAl/CFGG interface is better than that at the (001)-Ag/CFGG interface from our First-principles calculations of the ballistic transmittance. As, a result, the insertion of NiAl layers at Co2FeGa0.5Ge0.5/Ag interfaces effectively improved the intrinsic MR output; the highest ΔRA of 31 mΩμm2 (78 mΩμm2) and intrinsic MR ratio of 82% (285%) were obtained at room temperature (10 K), that are 2-3 times higher than those without NiAl insertion. Microstructure analysis using scanning transmission electron microscopy confirmed the existence of thin NiAl layers at the Ag interfaces with only modest inter-diffusion even after annealing at 550°C. The improvement of interfacial spin-dependent scattering by very thin NiAl insertion can be a predominant reason for the enhancement of MR output.
[1] M. Takagishi et al., IEEE Trans. Magn. 46, 2086 (2010).
[2] S. -C. Lui et al., Phys. Rev. B 42 1582 (1990).
[3] T. M. Nakatani. Spin-dependent scattering in CPP-GMR using Heusler alloy and the selection of the spacer material. PhD Thesis. University of Tsukuba (2011).
We have investigated the effect of the insertion of a thin NiAl layer (≤ 0.63 nm) to the Co2FeGa0.5Ge0.5(CFGG)/Ag interface on the MR properties in CFGG/Ag/CFGG devices. The Insertion layer of NiAl was selected because a good band structure matching between NiAl and Heusler compounds has been implied from the similar band dispersions along the <001> at k// = (0,0). [2,3] We also have clarified that the interfacial band matching at (001)-oriented NiAl/CFGG interface is better than that at the (001)-Ag/CFGG interface from our First-principles calculations of the ballistic transmittance. As, a result, the insertion of NiAl layers at Co2FeGa0.5Ge0.5/Ag interfaces effectively improved the intrinsic MR output; the highest ΔRA of 31 mΩμm2 (78 mΩμm2) and intrinsic MR ratio of 82% (285%) were obtained at room temperature (10 K), that are 2-3 times higher than those without NiAl insertion. Microstructure analysis using scanning transmission electron microscopy confirmed the existence of thin NiAl layers at the Ag interfaces with only modest inter-diffusion even after annealing at 550°C. The improvement of interfacial spin-dependent scattering by very thin NiAl insertion can be a predominant reason for the enhancement of MR output.
[1] M. Takagishi et al., IEEE Trans. Magn. 46, 2086 (2010).
[2] S. -C. Lui et al., Phys. Rev. B 42 1582 (1990).
[3] T. M. Nakatani. Spin-dependent scattering in CPP-GMR using Heusler alloy and the selection of the spacer material. PhD Thesis. University of Tsukuba (2011).