All-magnonic switching and spin-valve using antiferromagnetic magnons

In a collinear antiferromagnet (AF) with uniaxial anisotropy, symmetry guarantees that magnon excitations are doubly degenerate. The two degenerate modes carry opposite spin angular momentum and can play a similar role as spin-1/2 electrons. At an exchange coupled interface with a ferromagnet (F), thermal populations of the two modes are imbalanced, which can form a pure spin current that propagates under a thermal gradient. Here we present a theoretical framework of magnon transport in an insulating F/AF/F heterostructure. We find that a sufficiently large temperature gradient can switch the downstream F via magnon spin current in the AF if the system is initially prepared in an antiparallel configuration. This thermomagnetic switching opens the possibility of all-magnonic spin valve.