Spin mixing conductance (SMC) at the ferromagnetic/non-magnetic material (FM/NM) interface governs the transport efficiency of the spin current. A high level of SMC is crucial for efficient spin injection and spin manipulation. Here, we report a reliable way to enhance the SMC at the FM/NM interface by rare-earth doping in the NM layer. As evidenced by the decreased saturation magnetization in permalloy (Py)/Cu–Nd structures, an induced magnetism in Nd is proposed, which is likely to be antiferromagnetically coupled to Py at the interface. By changing the doping content of Nd, the Py/Cu–Nd interface can be well designed, which gives rise to an effective tuning of the SMC from 0.37 × 1015 to 16.26 × 1015 cm−2. Such a tuning effect of SMC is suppressed by inserting a Cu spacer, demonstrating the key role of the antiferromagnetically coupled interface to the improved SMC. Our results highlight the significance of rare-earth materials in spin transport, expanding the design capability of energy-efficient spintronic devices.
Bulk PtBi2 has attracted much attention for its topological semi-metallic electronic properties and highly promising applications in spintronics. Here, we report large spin–orbit torque (SOT) efficiency in the sputtered PtBi2 alloy with the trigonal-phase. From spin–torque-induced ferromagnetic resonance measurements, the SOT efficiency of 5 nm PtBi2 is estimated to be ∼0.2. Moreover, the spin Hall conductivity of PtBi2 [∼1 × 105 ℏ/2e (Ω m)−1] is comparable to that of topological materials, such PtTe2 and Bi2Te3. The PtBi2 film has much lower resistance than that of Bi-based topological materials, which makes it a useful candidate for application. The results suggest that the PtBi2 alloy is promising for applications in magnetic memory and logic devices driven by SOT.
Spin–orbit torque (SOT) has been extensively applied to magnetization manipulation in low power consumption logic and memory devices. However, it is believed that materials with strong spin–orbit coupling (SOC) are indispensable for magnetic torque generation. Recently, theoretical studies have indicated that the oxides of light materials with weak SOC can provide a sizable orbital torque (OT), inducing magnetization switching. Here, we experimentally report the extreme enhancement of torque efficiency and spin Hall angle through the natural oxidation of Cu with weak SOC in the perpendicularly magnetized Pt/Co/Cu–CuO x multilayers. The values of torque efficiency and spin Hall angle increase by approximately five times by tuning the surface oxidation at room temperature. The comparative analysis of the effective field reveals that the significant enhancement mainly originates from the collaborative drive of the OT at the Cu/CuO x interface and the SOT from the Pt layer. This finding provides a powerful way to engineer the high-efficient spintronic devices through combining OT and SOT to improve the torque efficiency.
In recent years, two-dimensional van der Waals (2D-vdW) magnets have been widely employed in spintronic devices since they can be reduced to the monolayer while maintaining structural integrity. In this paper, an interfacial effect of the heterostructure including the Co 60 Fe 20 B 20 (CFB) layer and Fe 3 GeTe 2 (FGT) flake is explored. At the Curie temperature (T c ) of FGT, a reduction in the magnetization of the CFB/FGT bilayer is found compared to that of CFB itself unlike at 300 K. It is possible that non-parallel magnetic moments are formed at the interface due to the strong perpendicular magnetic anisotropy (PMA) of magnetic FGT below T c . Using a ferromagnetic resonance technique, we find that both PMA and the magnetic damping of CFB are enhanced by the FGT interface. Particularly, the PMA constant K ⊥ is increased by 20.2% at 300 K, much larger than that at 150 K, which indicates that the enhancement of PMA is induced by orbital hybridization at the interface instead of the magnetic proximity effect. The exchange interaction at the interface for moments between CFB and FGT may play a minor role in the enhancement of PMA of CFB induced by FGT. Also, such a less PMA enhancement at 150 K may be blocked by the magnetic interface of FGT below T c . This research highlights that the magnetism of CFB can be modulated by the interface of FGT even at room temperature, which provides a new approach for the application of 2D-vdW magnets in spintronics.
The spin dynamics modulation has attracted extensive attention in the past decades. Rare-earth (RE) metals are essential participants in this context due to the large spin–orbit coupling. Here, with neodymium (Nd) capping, we achieve the enhancement on spin dynamic damping of Co40Fe40B20 (CFB) films by three times larger than that of CFB single layer. Based on the spin pumping theory, the interfacial spin mixing conductance [Formula: see text] is calculated as 7.3 × 1015 cm−2, which is one order larger than that of CFB/Pt. It leads to the large spin current transparency at CFB/Nd interface. By comparing of the resistivity of each layer, we found that the matched resistivity at two sides of the CFB/Nd interface plays an important role in the enhancement of [Formula: see text]. As a consequence, a high spin transparency of the CFB/Nd interface is obtained as 82%. In addition, damping enhancement of CFB is not changed promptly by inserting 1–2 nm Cu layer, but it is suppressed when the Cu layer is thicker than 3 nm, which is related to the thickness dependence of the Cu resistivity. Our study broadens the horizon for the application of rare-earth (RE) in spintronics.
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