Simultaneous enhancement of coercivity and saturation magnetization in high-performance anisotropic NdFeB thick films with a Dy diffusion layer.

Generally, the addition of the Dy element leads to a decrease of the saturation magnetization and the remanent magnetization in NdFeB films due to its antiferromagnetic coupling with Fe. However, in this study, upon increasing the ratio of Dy in the Nd-Dy diffusion layers of NdFeB thick films, the saturation magnetization has an anomalously slight enhancement, while the coercivity and remanent magnetization have a large enhancement. The increase of coercivity is attributed to the decoupling between Nd2Fe14B grains and the enhanced pinning effect. Microstructural analysis revealed a layered structure composed of spherical Nd2Fe14B grains at the location of the Dy diffusion layer, which is attributed to the Dy diffusion layer reacting with the region of Nd element aggregation during the annealing process, facilitating transformation into Nd2Fe14B grains. The increase of the proportion of Nd2Fe14B grains results in a slight enhancement of saturation magnetization. By this method, we obtained a high-performance anisotropic NdFeB thick film of 28.7 µm with a coercivity of 2.46 T and a surface field of 163 Oe. This work establishes a microscale growth model for NdFeB thick films and helps to prepare high-performance NdFeB thick films applicable directly to microelectromechanical systems.

Enhanced Spin-Orbit Torque and Low Critical Current Density in Pt100-xRux/[CoNi]/Ru Multilayer for Spintronic Devices.

Using a heavy-metal (HM) alloy layer in spin-orbit torque (SOT)-based devices is an effective method for obtaining a high current-spin conversion efficiency θSH. In this work, SOT-based spintronic devices with a Pt100-xRux-alloyed HM layer are studied by applying harmonic Hall measurements and magneto-optical Kerr effect microscopy to detect the θSH and to observe the process of current-induced magnetization switching. Both the highest θSH of 0.132 and the lowest critical current density (Jc) of 8 × 105 A/cm2 are realized in a device with x = 20, which satisfies the high SOT efficiency and low energy consumption simultaneously. The interfacial Dzyaloshinskii-Moriya interaction can be overcome by increasing the in-plane assist field. Meanwhile, the minimum in-plane field required for current-induced complete switching can be reduced to ±60 Oe. Our study reveals that using the Pt-Ru alloyed HM layer is an effective route for SOT application with enhanced performance.