Pressure-stabilized MnB6 that exhibits high-temperature ferromagnetism and high ductility at ambient pressure

Abstract

Metal borides are of significant interest because of their high strength, high melting point, superconductivity and magnetism. Here, a combination of swarm-intelligence structural search and first-principle calculations propose a pressure-stabilized hitherto unknown manganese boride, MnB₆, that is recoverable under ambient conditions and exhibits versatile properties. MnB₆ contains unique B_∞ ribbons along the c-axis, which are linked to each other in the a-b plane by B–B bonds to form open channels filled with Mn atoms. MnB₆ is ferromagnetic at its onset energetically stable pressure of 127 GPa and undergoes a transition from magnetic to superconducting at 160 GPa, with an estimated superconducting critical temperature of 15.9 K. Under ambient pressure, MnB₆ exhibits increased ferromagnetism with a magnetic moment of 1 μ_B per Mn atom and a Curie temperature as high as 520 K. Moreover, MnB₆ possesses good mechanical properties with an estimated Vickers hardness of 25 GPa and high ductility, which stems from the peculiar structural arrangements in MnB₆ driven by the ability of boron to form unusually versatile bonding states.