Magnetic and electronic properties ofCaMn2Bi2: A possible hybridization gap semiconductor

We report the magnetic and electronic properties of ${\mathrm{CaMn}}_{2}{\mathrm{Bi}}_{2}$, which has a structure based on a triangular bilayer of Mn, rather than the ${\mathrm{ThCr}}_{2}{\mathrm{Si}}_{2}$ structure commonly encountered for 122 compounds in intermetallic systems. ${\mathrm{CaMn}}_{2}{\mathrm{Bi}}_{2}$ has an antiferromagnetic ground state, with a ${\mathrm{T}}_{N}$ of 150 K, and for a 250 K temperature range above ${\mathrm{T}}_{N}$ does not exhibit Curie-Weiss behavior, indicating the presence of strong magnetic correlations at high temperatures. Resistivity measurements show that ${\mathrm{CaMn}}_{2}{\mathrm{Bi}}_{2}$ 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 ${\mathrm{CaMn}}_{2}{\mathrm{Bi}}_{2}$, examined via ab-initio electronic structure calculations, indicates that Mn 3d orbital hybridization is essential for the formation of the band gap, suggesting that ${\mathrm{CaMn}}_{2}{\mathrm{Bi}}_{2}$ may be a hybridization-gap semiconductor.