The field of spintronics, or magnetic electronics, is maturing and giving rise to new subfields. These new directions involve the study of collective spin excitations and couplings of the spin system to additional degrees of freedom of a material, as well as metastable phenomena due to perturbations that drive the system far from equilibrium. The interactions lead to possibilities for future applications within the realm of energy-efficient information technologies. Examples discussed herein include research opportunities associated with (i) various spin-orbit couplings, such as spin Hall effects, (ii) couplings to the thermal bath of a system, such as in spin Seebeck effects, (iii) spin-spin couplings, such as via induced and interacting magnon excitations, and (iv) spin-photon couplings, such as in ultrafast magnetization switching due to coherent photon pulses. These four basic frontier areas of research are giving rise to new applied disciplines known as spin orbitronics, spin caloritronics, magnonics, and spin photonics, respectively. These topics are highlighted in order to stimulate interest in the new directions that spintronics research is taking and to identify open issues to pursue.

• Received 4 June 2015

DOI:https://doi.org/10.1103/PhysRevApplied.4.047001