Metamagnetic transition in EuFe2As2 single crystals

We report the measurements of anisotropic magnetization and magnetoresistance on single crystals of EuFe2As2, a parent compound of ferro-arsenide hightemperature superconductor. Apart from the antiferromagnetic (AFM) spin-densitywave transition at 186 K associated with Fe moments, the compound undergoes another magnetic phase transition at 19 K due to AFM ordering of Eu spins (J = S = 7/2). The latter AFM state exhibits metamagnetic transition under magnetic fields. Upon applying magnetic field with H ‖ c at 2 K, the magnetization increases linearly to 7.0 μB/f.u. at μ0H=1.7 T, then keeps at this value of saturated Eu 2+ moments under higher fields. In the case of H ‖ ab, the magnetization increases step-like to 6.6 μB/f.u. with small magnetic hysteresis. A metamagnetic phase was identified with the saturated moments of 4.4 μB/f.u. The metamagnetic transition accompanies with negative in-plane magnetoresistance, reflecting the influence of Eu moments ordering on the electrical conduction of FeAs layers. The results were explained in terms of spin-reorientation and spin-reversal based on an A-type AFM structure for Eu spins. The magnetic phase diagram has been established. PACS numbers: 74.10.+v; 75.30.Kz; 75.30.Cr; 75.47.Pq Metamagnetic transition in EuFe2As2 2