Anisotropy of Superconducting Single Crystal SmFeAsO0.8F0.2 Studied by Torque Magnetometry

Single crystals of the oxypnictide superconductor SmFeAsO0.8F0.2 with T (c)a parts per thousand integral 45(1) K were investigated by torque magnetometry. The crystals of mass a parts per thousand currency sign0.1 mu g 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 gamma was found to be field independent, but varies strongly with temperature ranging from gamma a parts per thousand integral 8 at Ta parts per thousand T-2 (c) to gamma a parts per thousand integral 23 at Ta parts per thousand integral 0.4T (c). This unusual behavior of gamma signals unconventional superconductivity.