Spin-orbit torque is not only a useful probe to study manipulation of magnetic textures and magnetic states at the nanoscale but also it carries great potential for next-generation computing applications. Here we report the observation of rich spin-orbit torque switching phenomena such as field-free switching, multistate switching, memristor behavior and ratchet effect in a single shot, co-sputtered, rare earth-transition metal GdxCo100−x. Notably such effects have only been observed in antiferromagnet/ferromagnet bi-layer systems previously. We show that these effects can be traced to a large anistropic canting, that can be engineered into the GdxCo100−x system. Further, we show that the magnitude of these switching phenomena can be tuned by the canting angle and the in-plane external field. The complex spin-orbit torque switching observed in canted GdxCo100−x not only provides a new platform for novel spintronics but also serves as a model system to study the underlying physics of complex magnetic textures and interactions.

Spin-orbit torque (SOT) shows great potential for next-generation memory technology. Conventionally, the underlying physics of SOT has been associated with heavy (high-Z) elements and/or intrinsic bandstructure. Here, we report large spin-orbit torques in amorphous iron silicides, a material that involves only light elements and for which an E-k relationship cannot be defined. We have achieved a spin-orbit torque efficiency as high as 2.0 (i.e. 200%), which is comparable to the highest known spin-orbit torque efficiency material system (topological insulator). We also found that the SOT efficiency shows a functional dependence on the relative position of the Fermi level with respect to the density of states, indicating an intrinsic origin. In addition, the SOT efficiency does not follow the decreasing trend with increasing conductivity as is typically found in conventional materials. The conventional trend makes it difficult to alter the product of SOT efficiency and conductivity, thereby limiting the overall efficiency of a SOT device. Our results demonstrate a new class of material system, amorphous silicides, where it is possible to generate strong spin currents and where the underlying physics of spin current generation is very different, allowing to circumvent some of the fundamental limitations of conventional materials.

We demonstrate coherent spin physics of a single tin vacancy center (SnV−) in diamond pillars including coherent population trapping and Rabi oscillations. This work constitutes progress towards scalable quantum networks using SnV− centers.