Anisotropy of superconducting single crystal SmFeAsO(0.8)F(0.2) studied by torque magnetometry

Abstract

Single crystals of the oxypnictide superconductor SmFeAsO(0.8)F(0.2) with Tc=45(1) K were investigated by torque magnetometry. The crystals of mass~0.1 mug were grown by a high-pressure cubic anvil technique. The use of a high-sensitive piezoresistive torque sensor made it possible to study the anisotropic magnetic properties of these tiny crystals. The anisotropy parameter was found to be field independent, but varies strongly with temperature ranging from 8 at T=Tc to 23 at T=0.4Tc. This unusual behavior signals unconventional superconductivity.