Colossal Magnon Magnetoresistance of Two-Dimensional Magnets

The magnon current holds substantial importance in facilitating the transfer of angular momentum in spin-based electronics. However, the magnon current in three-dimensional magnetic materials remains orders of magnitude too small for applications. In contrast, magnon numbers in two-dimensional systems exhibit significant enhancement and are markedly influenced by external magnetic fields. Here, we investigate the magnon current in a two-dimensional easy-axis ferromagnet and find a colossal magnon magnetoresistance (CMMR) effect, wherein the change of the magnon conductance can reach as high as a thousand percent in a moderate magnetic field. Moreover, the magnitude of the CMMR exhibits significant dependence on the orientation of the magnetic field due to the interplay between magnon- conserving and non-conserving scattering. We propose a non-local magnon-mediated electrical drag experiment for the possible experimental observation of the predicted effect. With the CMMR effect and a much larger magnon number, magnon current in 2D materials shows promise as a primary source for spin transport in spintronics devices.9