[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

9:45 〜 10:00英語発表

[17a-D61-4] Enhanced tunnel magnetoresistance of Fe/MgGa₂O₄/Fe(001)
magnetic tunnel junctions using MgO terminations as a Ga diffusion barrier

〇(D)Rombang Rizky Sihombing^1,2, Thomas Scheike¹, Zhenchao Wen¹, Jun Uzuhashi¹, Tadakatsu Ohkubo¹, Seiji Mitani^1,2, Hiroaki Sukegawa¹ (1.NIMS, 2.Univ. Tsukuba)

キーワード：

Spintronics、Tunnel magnetoresistance (TMR)、MgGa2O4

Magnetic tunnel junctions (MTJs) are widely used in spintronic applications, including tunneling magnetoresistive (TMR) heads in hard disk drives and magnetoresistive random access memory (MRAM) cells. Recently, it has been reported that MgO insertion at both the upper and lower MgGa₂O₄ (MGO) interfaces in CoFeB/MGO/CoFeB MTJs is effective in enhancing the interfacial perpendicular magnetic anisotropy and TMR ratio. However, the mechanism of the improvement by the insertion remains to be elucidated. In this study, we developed Fe/MGO/Fe(001) epitaxial MTJs to investigate the effect of the MgO termination. MTJ stacks were deposited by ultra-high vacuum magnetron sputtering. The typical structure is MgO(001) substrate/Cr buffer/Fe(50)/bottom MgO/MGO (1.7)/top MgO/Fe (5)/IrMn (10)/Ru (10), (unit: nm). The MgO and MGO layers were deposited using MgO and MgGa₂O₄ sintered targets. The insertion of MgO ~0.3 nm for the bottom and top MGO interfaces and post-annealing processes resulted in an enhanced TMR ratio of 151% at RT. The value increases up to 291% at 5 K. Scanning transmission electron microscopy and energy dispersive X-ray spectroscopy of the MTJ cross-section revealed that Ga diffusion from the MGO to the Fe layers is suppressed by the MgO insertion, improving the TMR ratio.