[9p-M101-1~7] 10.1 Emerging materials in spintronics and magnetics (including fabrication and charactrization methodologies)

▲ [9p-M101-6] Electronic and magnetic properties of graphene/Co₂Fe(Ge_0.5Ga_0.5) Heusler alloy heterostructure

〇(P)Songtian Li¹, Konstantin V. Larionov², Zakhar I. Popv², Yoichi Yamada³, Kenta Amemiya⁴, Shiro Entani¹, Yuya Sakuraba⁵, Hiroshi Naramto¹, Pavel B. Sorokin², Seiji Sakai¹ (1.QST, 2.NUST MISiS, 3.Univ. of Tsukuba, 4.KEK, 5.NIMS)

Keywords:Heusler alloy, Graphene, Spin-valve

As a zero-gap semiconductor with a pin-hole free nature, graphene was proposed as an attractive low energy barrier for vertical spin-valves (SV) to solve the trade-off between MR ratio and low RA product usually observed in MgO-based vertical SV. So far, the MR ratio reported in graphene-spacer vertical SV is far below the application level due to the usage of conventional ferromagnetic electrodes (Ni, Co, Fe etc.) with low spin polarization. Utilizing high spin-polarized ferromagnetic electrodes such as full Heusler alloys is potential way to enhance the MR ratio in graphene-spacer SV, however, there is no precedent for success in the growth of graphene on Heusler alloy underlayer. In this study, we report on the demonstration and characterization of a novel heterostructure consisting of single-layer graphene (SLG) synthesized by high-vacuum chemical vapor deposition (CVD) on a half-metallic Co₂Fe(Ge_0.5Ga_0.5) (CFGG) Heusler alloy, which provides a promising building block for developing high performance graphene-spacer vertical SV.
Fig. 1 shows the surface characterization results of SLG/CFGG/MgO(001) by a, b) RHEED, and c) STM. The sharp RHEED streaks indicate an atomically flap surface of CFGG at the SLG/CFGG interface. The periodic strips in the STM image is attributed to the Moire superstructure resulted from the lattice miss-match between graphene and CFGG(001), indicating the growth of single crystalline SLG on CFGG. Fig. 2 shows the result of the depth-resolved XMCD analysis of the Co L_2,3-edge in the SLG/CFGG heterostructure. A robust magnetization was observed in the region just below the SLG/CFGG interface, which indicates little degradation of the magnetic property of the CFGG surface after the CVD-graphene growth. The effect of SLG on the half-metallicity of the CFGG surface will be also discussed in the presentation.