講演情報
[14p-K302-7]First-principles study of disordered effects and composition dependence on transport properties in Co2FeGa0.5Ge0.5-CuZn based CPP-GMR devices
〇(D)Kodchakorn SIMALAOTAO1,2, Ivan Kurniawan2, Yoshio Miura2,3, Yuya Sakuraba1,2 (1.Univ. of Tsukuba, 2.NIMS, 3.KIT)
キーワード：
CPP-GMR、Disordered effects and composition dependence、First-principles calculations
CPP-GMR devices are promising candidates for next-generation HDD read heads due to their low resistance-area product (RA) and high-speed compatibility. Building on our previous work, we conducted a systematic search of Cu-X binary spacers and identified CuZn as the optimal candidate for integration with half-metallic Co2FeGa0.5Ge0.5 (CFGG) electrodes. This was attributed to their significant conductive states, particularly around the k|| = (0,0) in the Brillouin zone, and their good Fermi surface matching with CFGG electrodes. In this study, we extend the investigation to explore the effects of atomic disorder and composition dependence in CuZn spacers on the majority-spin ballistic conductance, inversely proportional to interfacial resistance. Across the degree of disorder x (0 ≤ x ≤ 1), where the CuZn spacer transitions from B2 (Zn-terminated) to A2 and finally to B2 (Cu-terminated) structures, the conductance was observed to strongly depend on both the degree of disorder and the termination type at the CFGG/CuZn interface. For FeGe- and FeGa-terminated configurations, the conductance increases linearly with disorder degree x, while Co-terminated structures show a weaker dependence. Among all configurations, the B2-ordered Cu-terminated spacer with FeGa termination shows the highest conductance enhancement, approximately 3%, compared to the A2-disordered spacer. In addition, the compositional dependence of Cu1-yZny (0 ≤ y ≤ 1) spacers was analyzed for B2- and A2-type structures. The results indicate that majority-spin ballistic conductance is maximized at approximately 35–50% Zn content for both structure types. These findings highlight the critical role of atomic disorder and composition in determining transport properties, offering key insights for the atomic-scale design of spacer materials and interfaces in high-performance CPP-GMR devices.