Magnetic and electronic properties of CaMn2Bi2: A possible hybridization gap semiconductor

Abstract

We report the magnetic and electronic properties of CaMn2Bi2, which has a structure based on a triangular bilayer of Mn, rather than the ThCr2Si2 structure commonly encountered for 122 compounds in intermetallic systems. CaMn2Bi2 has an antiferromagnetic ground state, with a T-N of 150 K, and for a 250 K temperature range above TN does not exhibit Curie-Weiss behavior, indicating the presence of strong magnetic correlations at high temperatures. Resistivity measurements show that CaMn2Bi2 exhibits semiconducting properties at low temperatures, with an energy gap of only 62 meV, indicating it to be a very narrow band gap semiconductor. The electronic structure of CaMn2Bi2, examined via ab-initio electronic structure calculations, indicates that Mn 3d orbital hybridization is essential for the formation of the band gap, suggesting that CaMn2Bi2 may be a hybridization-gap semiconductor.