Low-field reorientation transition and anisotropic orientational order of vortex lattices in LuNi2B2C -: art. no. 220508

Vortex lattices in as-grown and annealed LuNi2B2C single crystals were studied by high resolution Bitter decoration in fields up to 2000 Oe. The reorientation transition between two different rhombic structures is recorded at H(1)approximate to 250 Oe in annealed crystals in which the transition to the square lattice occurs at H-2 approximate to 500 Oe, which is lower than for as-grown crystals. A strongly anisotropic orientational order is discovered in the vicinity of H-2, These results are discussed in the framework of the nonlocal London model.