Magnetic properties of field-induced superconductor, κ-(BETS)2FeBr4

Magnetic torque of the two-dimensional organic superconductor, kappa-(BETS)(2)FeBr4 was measured at 30mK under field B up to 17.5 T. In B perpendicular to layers, the field dependence of the torque shows a step-like kink at 5.5 T, which corresponds to the transition from the canted antiferromagnetic (AF) to the paramagnetic state. In B vertical bar vertical bar a (magnetic easy axis), we observed very anomalous torque curves, which are probably reflecting the successive magnetic transitions of the Fe 3d spins. The angular dependence of the torque in the AF state is discussed in terms of the uniaxial magnetic anisotropy of the 3d moments. (c) 2005 Elsevier B.V. All rights reserved.