Hardness, magnetic, elastic, and electronic properties of manganese semi-boride synthesized by high pressure and high temperature

Abstract

Transition metal (TM) interaction induces many fantastic properties in transition metal light element compounds (TMLEs). Here, we report the synthesis of polycrystalline Mn2B specimen with strong Mn–Mn interaction by high pressure and high temperature (HPHT) method. Magnetic characterization gives anti-ferromagnetic and spin-glass behavior with Néel temperature of 43 ​K. Micro-hardness measurement yields an asymptotic Vickers hardness of 14.1 ​GPa which is far higher than manganese metal. To interpret the mechanical and magnetic properties, the chemical bond and electronic structure were investigated by first principle calculation. Although the distance between manganese atoms has been enlarged by inserting boron atoms, anti-ferromagnetic behavior is attributed to the insufficient Mn–Mn distance enlargement. Based on the bonds character, these manganese atoms layers are pinned together by quasi-boron-chains which is contradictory with fully isolated boron atoms configuration. Quasi-covalent boron chains and partial covalent Mn–B bonds attribute to its high hardness. Tuning Mn–Mn interaction is demonstrated as a promising method to modulate d-electron related magnetic and hardness property.