Pressure-Induced First-Order Antiferromagnetic to Ferromagnetic Transition in Mnn

MnN systems have been widely used to investigate Mn incorporated into Ш–V compounds, which combines the spin and electron charge as promising diluted magnetic semiconductors (DMS). However, few experiments have demonstrated the magnetic transformation of MnN with lattice constant changes, although it has been mentioned many times in previous theoretical calculations. In this study, we synthesize MnN single crystal under high pressure and temperature. Furthermore, we perform high-pressure resistance, magnetic resistance and synchrotron radiation on MnN single crystal/polycrystalline and observe the first-order phase transition accompanied with antiferromagnetic (AFM) to ferromagnetic (FM) magnetic structure transition under 34 GPa. The experimental result and first-principles calculations reveal the same magnetic and structural transition of MnN in the compression process from equilibrium volume 18.2 to16 Å3. An analysis of electronic structure and magnetic interactions in terms of the Heisenberg Hamiltonian indicates a strong FM coupling in the [001] plane due to the double exchange mechanism of Mn eg orbitals. With the reduced Mn-N bond length under high pressure, the enhanced FM double exchange interactions could induce the magnetic transition from AFM to FM and subsequently lead to a structural transition from a face-centered tetragonal structure to a cubic structure. These findings provide the foundations for GaMnN or MnN layer DMS.