Efficient Spintronics with Fully Compensated Ferrimagnets

Conventional spintronics exploit predominately the properties of ferromagnets (FM). The functionalities of the related devices suffer from two detrimental aspects including the stray fields and the gigahertz (GHz) spin dynamics. These intrinsic limits of FMs can be overcome in antiferromagnets (AFMs), resulting from their vanished stray field, and the faster dynamics in the terahertz (THz) range. On the other hand, AFMs are typically inert to the external magnetic fields. A reliable writing, and more importantly, an accurate read-out of these AFM states are often experimentally challenging, which impede their technological applications. By contrast, ferrimagnets (FIMs) exhibit two antiparallel lattices, and the magnetism of these two sublattices can be fully compensated that manifests as AFM-like dynamics. Unlike the weak resistive response of AFMs, the spin transport properties in FIMs is dominated by one particular lattice (or element). One can thus utilize the typical resistive measurements to unambiguously explore the ultrafast spin dynamics of FIMs. Based on the rare-earth iron garnets (RE3Fe5O12), the rare earth-transition metal (RE-TM) alloys and the rare-earth-free nitrided manganese (Mn4N), we will discuss the characteristic properties of the fully compensated ferrimagnetism and their resulting efficient spin dynamics. It is expected that the present review article could excite renowned interests in the compensated FIMs, which could be beneficial for developing the ultrafast spintronic memories and logics.