Impact of magnetic fields on anisotropy in Ca3Ru2O7 -: art. no. 094427

Ca3Ru2O7 is a bilayered metallic paramagnet that orders antiferromagnetically at T-N = 56 K while remaining metallic and then undergoes a spin reorientation coincident with a metal-nonmetal transition at T-M = 48 K, entering a metamagnetic state. Low-temperature specific-heat measurements in magnetic fields show that the electronic specific heat, gamma = 44 mJ/mol K-2, is field independent above and below the 6-T critical field, whereas the first-order nature of the metamagnetic transition is reflected by a small shift in the Debye temperature. Magnetization, electrical resistivity, and specific-heat measurements were performed on high-quality single crystals, allowing construction of detailed H-T phase diagrams, which differ considerably for magnetic fields applied along the two in-plane directions. These measurements led to determination of the anisotropy field H-A = 22.4 T and exchange field H-E = 14.2 T. Evidence is presented for a possible flopside state in the region above the 41-K and 5.5-T multicritical point. Finally, superheating and supercooling are observed at temperatures and magnetic fields slightly above the multicritical point.