Spin-orbit torques (SOTs) describe the current-induced magnetic torques originating from the spin-orbit coupling of conduction electrons in the bulk and interfaces of materials. First demonstrated experimentally in semiconductors and then in metals, SOTs have attracted enormous attention from the spintronics and community due to their immense potential and flexibility in manipulating magnetization by electricity.
Magnetic anisotropy is the tendency for the magnetization to point along certain preferential axes in a magnetic material. It is an important property for spintronic devices as the magnetic data can be encoded in the magnetization orientation, taking two equally stable values (e.g., up -> 1, down -> 0). There is an energy barrier associated with reversing the magnetization between these two stable states.
Early breakthrough discoveries in spintronics, namely the giant and tunnel magnetoresistance effects, magnetic interlayer coupling, interfacial perpendicular magnetic anisotropy (PMA), and spin-transfer-torques (STT), exclusively relied on conducting magnetic materials such as Co, Fe, and Ni. Due to the lack of knowledge and methods to electrically probe and control magnetization, magnetic insulators remained less explored in the spintronics context up until recently.
Information technologies are rapidly evolving. We need more powerful computers, larger data storage capabilities, and faster reading, writing, and digital data processing. Therefore, we are in a continuous quest to shrink the size of memory elements and find more efficient ways to process the data without compromising an increasing energy and material cost. Spintronics offers one of the most viable solutions to these endeavors, and consequently, has become a prominent field of research in the past 35 years.