Metamagnetism and 1/3 Plateau in the Spin Chain Compound CoV2O6

The pseudo-one dimensional brannerite type compound CoV2O6 has been studied by magnetisation and heat capacity measurements in the temperature range 1.8 < T < 300 K and in applied fields of up to 9 T. Our measurements show an unusual balance of exchange interactions (CW= 2.8(2) K) and a single antiferromagnetic transition at TN = 7 K. M(H) isotherms recorded below 5 K show a metamagnetic transition and a 1/3 magnetisation plateau. From 5-7 K, only the metamagnetic transition is observed. For T < TN < ~ 25 K, our heat capacity and magnetisation measurements show evidence for strong low dimensional ferromagnetic fluctuations. We propose a simple phase diagram, discuss the principle features and emphasise the importance of Ising anisotropy.