講演情報
[11a-E208-2]Highly effective and external-field-free spin-orbit torque switching of CoFeB/MgO using hybrid in-plane ferromagnet/BiSb topological insulator
〇(P)HOANGHUY HO1, NAMHAI PHAM1 (1.Institute of Science Tokyo)
キーワード：
topological insulator、magnetization switching、spin-orbit torque
Realization of type-z spin-orbit torque (SOT) magnetoresistive random-access memory (MRAM) requires both highly effective spin Hall material for low-power operation and field-free magnetization switching. So far, the former has been addressed by using topological materials such as topological insulators and topological semimetals. In this matter, BiSb topological insulator has emerged as a promising candidate thanks to its superior spin Hall angle of 10-52 and relatively high conductivity of 1.5-2.5×105 Ohm-1m-1. Meanwhile, the latter requires symmetry breaking by introducing canted ferromagnetic free layers, strong dipole coupling from hard mask, dynamic Dzyaloshinskii - Moriya interaction, and unconventional spin torques using both σx and σz spins reported in low-symmetry materials. For commercialization, field-free SOT switching should be achieved with high uniformity and scalability on 300-mm Si wafers.
In this work, we demonstrate both highly effective and external-field-free SOT switching of CoFeB/MgO using hybrid in-plane ferromagnet/BiSb topological insulator layers. We realize a large spin Hall angle of 7.7 and conductivity of 1.0×105 Ohm-1m-1 for BiSb in a sputtered stack of Si/SiO2 substrates /Ti 3.0 nm/Ta 1.0 nm/Co19Fe56B25 1.0 nm/MgO 2.0 nm/(Ta 0.2 nm/Co 0.2 nm)2/Ta 0.2 nm/top BiSb 10 nm/MgO 1.0 nm/Ta 2.0 nm cap. Furthermore, the stray field from the (Ta 0.2 nm/Co 0.2 nm)2 in-plane ferromagnetic layer allows the external-field-free magnetization switching with an internal in-plane bias field of ± 45 Oe for CoFeB. Our work provides a strategy for designing low-power and external-field-free magnetization switching in z-type SOT-MRAM stacks.
In this work, we demonstrate both highly effective and external-field-free SOT switching of CoFeB/MgO using hybrid in-plane ferromagnet/BiSb topological insulator layers. We realize a large spin Hall angle of 7.7 and conductivity of 1.0×105 Ohm-1m-1 for BiSb in a sputtered stack of Si/SiO2 substrates /Ti 3.0 nm/Ta 1.0 nm/Co19Fe56B25 1.0 nm/MgO 2.0 nm/(Ta 0.2 nm/Co 0.2 nm)2/Ta 0.2 nm/top BiSb 10 nm/MgO 1.0 nm/Ta 2.0 nm cap. Furthermore, the stray field from the (Ta 0.2 nm/Co 0.2 nm)2 in-plane ferromagnetic layer allows the external-field-free magnetization switching with an internal in-plane bias field of ± 45 Oe for CoFeB. Our work provides a strategy for designing low-power and external-field-free magnetization switching in z-type SOT-MRAM stacks.