Room-Temperature Ferromagnetism and Strain-dependent Magnetic Anisotropy in 2D MnGaN

Abstract

Two-dimensional magnetic materials are of great interest for fundamental science and advanced applications while dilute magnetic semiconductors captured worldwide interest by combining magnetism with electronics. MnGaN-2D is an ultimately-thin, 2D-DMS material, consisting of a dense, well-ordered layer of Mn, Ga, and N atoms. MnGaN-2D shows room-temperature ferromagnetism as previously demonstrated with spin-polarized scanning tunneling microscopy as a function of applied magnetic field. This was also predicted by first-principles theoretical calculations which reveal the origins of the ferromagnetism through its highly spin-split and spin-polarized electronic structure.[1] The SP-STM results are recently confirmed by SQUID magnetometry which reveals perpendicular magnetic anisotropy and a high spin-polarization of ∼79% at room temperature.[2] New results for this novel system also suggest the possibility of magneto-elasticity. Theoretical calculations reveal sensitivity of the spin polarization to lattice strain. Spin-orbit coupling is included in the calculations, which indicate either out-of-plane or in-plane anisotropy, dependent on the type of strain whether compressive or tensile. Clear evidence for both compressive and tensile local lattice strains is found by detailed analysis of atomic resolution STM images which reveal a wide, non-Gaussian range of lattice spacings (-18% to + 18% variations), unlike normal materials. Furthermore, scanning tunneling spectroscopy measurements, showing the spin-polarized filled states manganese peak, find fluctuations in the electronic position of the peak from spectrum to spectrum. The FSMP position is also found to fluctuate, depending on lattice strain, in the theoretical calculations, thus indicating a connection between electronic states and magnetic anisotropy in this RT ferromagnetic 2D layer.