Magnetic, transport, and thermodynamic properties of CaMn2O4 single crystals

Physical properties including magnetic susceptibility, room-temperature electrical resistivity, thermal conductivity, heat capacity, and thermal expansion are reported for high quality single-crystal samples of marokite CaMn2O4. We determined that CaMn2O4 is highly electrically insulating and exhibits long-range antiferromagnetic order below T-N=217.5 +/- 0.6 K with easy axis along a. Anisotropic thermal expansion, similar to that of crystallographically layered materials, is observed, suggesting that the crystal structure of CaMn2O4 is also assembled from previously undescribed layers. An extensive thermodynamic study of the antiferromagnetic transition was undertaken resulting in a heat-capacity critical exponent alpha=0.082 +/- 0.007 and calculated pressure derivative dT(N)/dP=5.154 +/- 0.174 K/GPa.