Room-temperature spin valve effect in the TiCr2N4 monolayer

The van der Waals spin valve, usually consisting of two ferromagnetic layers separated by a nonmagnetic layer, is potentially useful for low-dimensional spintronic devices. Can the spin valve effect be realized in a monolayer van der Waals material? Motivated by the recent synthesis of the MoSi2N4 monolayer and WSi2N4 monolayer, we investigate the spin valve effect in the TiCr2N4 monolayer based on density functional theory and Boltzmann transport theory. The TiCr2N4 monolayer retains a ferromagnetic ground state above room temperature, whose electrical transport property is strongly dependent on the angle of magnetization direction between the two Cr atomic layers. As the angle increases, the conductivity reduces dramatically and results in giant magnetoresistance in the TiCr2N4 monolayer. The serious reduction of conductivity originates from the enlargement of the band gaps, which results in appreciable reduction of the electron group velocity and carriers near the Fermi level. The large difference in conductivity between the TiCr2N4 monolayers with parallel and anti-parallel magnetization makes it an ideal candidate for spin valve devices. Our results reveal the potential opportunities of a ferromagnet with monolayer limitations for spintronics and a unique platform for exploring fundamental physics.