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

Abstract

Single crystals of the oxypnictide superconductor SmFeAsO 0.8F 0.2 with T c≃45(1) K were investigated by torque magnetometry. The crystals of mass ≤0.1 μg 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 γ was found to be field independent, but varies strongly with temperature ranging from γ≃8 at T≲T c to γsime;23 at Tsime;0.4T c. This unusual behavior of γ signals unconventional superconductivity. © 2008 Springer Science+Business Media, LLC.