[17a-D61-1~10] 10.3 スピンデバイス・磁気メモリ・ストレージ技術

9:00 〜 9:15英語発表

[17a-D61-1] Searching for Cu-X spacers with a half-metallic Co₂FeGa_0.5Ge_0.5 electrode to boost magnetoresistance in CPP-GMR devices using first-principles calculations

〇(D)Kodchakorn SIMALAOTAO^1,2, Ivan Kurniawan², Yoshio Miura^2,3, Yuya Sakuraba^1,2 (1.Univ. of Tsukuba, 2.NIMS, 3.KIT)

キーワード：

CPP-GMR、Cu-based binary alloys、First-principles calculations

Current-perpendicular-to-plane giant magnetoresistive (CPP-GMR) devices are considered promising candidates for the next-generation magnetic read heads in hard disk drives (HDDs). These devices benefit from a small resistance-area product (RA), which is advantageous for compact read heads and high-speed reading. Co₂FeGa_0.5Ge_0.5 (CFGG) is a prominent half-metallic Heusler alloy known for achieving a high magnetoresistance (MR) ratio in CPP-GMR devices with Ag spacers^1-3. To further enhance the MR ratio in CPP-GMR devices, we investigate the potential of Cu-based binary alloys (Cu-X) as spacers compared to a traditional Ag spacer. To this end, we employ first-principles calculations to compare the interface resistance in CFGG/Ag/CFGG(001) and CFGG/Cu-X/CFGG(001) trilayers. We focus on majority-spin interface ballistic conductance, which is inversely proportional to the interface resistance, based on the Landauer formula. Our calculations show that Cu-X spacers exhibit a lower interface RA compared to the Ag spacer, indicating a significant improvement in the MR ratio. In particular, the RA of the CFGG/CuZn(001) interface is about 30% smaller than that of the CFGG/Ag(001) interface in all the interfacial terminations at its maximum difference, indicating the advantage of the CuZn spacer for obtaining a large MR ratio in the CPP-GMR devices. Fig. 1 indicates a significant conductive predominance of the CuZn spacer, especially around the k_|| = (0,0) in the Brillouin zone, with a good Fermi surface matching with the CFGG electrode. In addition, CFGG/CuZn/CFGG(001) exhibits lower formation energies in all interfacial terminations, indicating superior structural stability compared to CFGG/Ag/CFGG(001). Consequently, among the various Cu-X spacers examined, CuZn emerged as the most optimal candidate for a half-metallic CFGG electrode.