Angular dependences of the motion of the anisotropic flux line lattice and the peak effect inMgB2

Abstract

We have studied the angle-dependent motion of the anisotropic flux line lattice (FLL) and the peak effect (PE) inMgB2 single crystals. Forarbitrary angles (θ), wemeasured the resistance (R(H)) and critical current (Ic(H)) with AC and DC currents, respectively. At low fields below the PE,R(H) and Ic(H) showed a weak angular dependence, regardless of the type of excitationcurrent, because of the stable vortex state. At intermediate fields near the PE,R(H) andIc(H) at the onset of thePE varied with θ, depending on the type of external current, due to the metastability of the disorderedvortex lattice near the PE. At high fields above the PE and near the upper critical fieldHc2,the R(H) curves showed a simple scaling behavior withθ.