Large tunneling magnetoresistance in room temperature magnetic tunnel junctions based on altermagnetic XV2Y2O

This work presents a comprehensive investigation of spin-dependent quantum transport properties of the emerging layered room temperature metallic altermagnet family X V 2 Y 2 O ( X = K, Rb, Cs; Y = S, Se, Te), based on first-principles calculations combined with the non-equilibrium Green’s function formalism. Two magnetic tunnel junctions (MTJs) are designed: one with altermagnetic X V 2 Y 2 O electrodes and another with non-magnetic metallic electrodes. For the former, we examine both conventional MgO barriers and a newly proposed class of lattice-matched insulating barriers X 2 Y . We demonstrate that conventional MgO barriers suffer from quantum-well resonances in the thin-barrier regime due to anomalous interface reflections. MTJs with X 2 Y barriers exhibit a generally increasing tunneling magnetoresistance (TMR) trend with barrier thickness, governed by the distinct decay rates of the parallel and antiparallel configurations. Additionally, interfacial engineering could modulate device performance. In the metal-electrode MTJs, the transmission coefficient is larger than in the altermagnetic-electrode case, yielding significantly larger current while still maintaining a high TMR ratio exceeding 10 6 %. Our results establish X V 2 Y 2 O as a versatile materials platform for high-performance MTJs, providing clear design principles for the development of room temperature altermagnet-based spintronic devices.