Effects of magnetic field and pressure on the antiferromagnetic and weak-ferromagnetic orders in tetrahedral spin chain system Cu3Mo 2O9

Abstract

We study effects of magnetic field and pressure on the magnetic orders in Cu3Mo2O9, which shows an antiferromagnetic phase transition at TN = 7.9 K and a weak ferromagnetic one at T c ≃ 2.5 K. These successive phase transitions originate from the frustrations in the tetrahedral spin structure. The result of the heat capacity indicates that TN increases with applying magnetic field H up to 6 T and then saturates for H || a, and it shows a bow-shaped curve for H || c. On the other hand, for the easy axis, i.e., for H b it does not change up to 9 T. We also study the temperature dependence of magnetic susceptibility and magnetization curve under hydrostatic pressures below 1.0 GPa. The result suggests that Tc rapidly increases with increasing pressure up to 0.1 GPa and then drastically decreases, keeping TN almost unchanged. These results are discussed in terms of the change of the frustrations. © 2010 IOP Publishing Ltd.