Angular dependences of the motion of the anisotropic flux line lattice and the peak effect in MgB₂

We have studied the angle-dependent motion of the anisotropic flux line lattice (FLL) and the peak effect (PE) in MgB2 single crystals. For arbitrary angles theta, we measured the resistance (R(H)) and critical current (I-c(H)) with AC and DC currents, respectively. At low fields below the PE, R(H) and I-c(H) showed a weak angular dependence, regardless of the type of excitation current, because of the stable vortex state. At intermediate fields near the PE, R(H) and Ic(H) at the onset of the PE varied with theta, depending on the type of external current, due to the metastability of the disordered vortex lattice near the PE. At high fields above the PE and near the upper critical field H-c2, the R(H) curves showed a simple scaling behavior with.