The vortex lattices in LuNi2B2C single crystals

Vortex lattices in LuNi2B2C have been investigated by the decoration method at fields 20–1000 Oe at liquid helium temperatures and in a field cooling regime. At small fields of 20–200 Oe we have observed vortex lattice domains with different lattices orientations. Domains size increased with magnetic field increase. At low fields vortex lattices closepacked directions in small domains do not correlate with crystal directions and the correlations become stronger at greater fields. One of the closepacked vortex arrays directions within a domain becomes parallel to 〈1 1 0〉 or 〈1 0 0〉 directions. The vortex lattices themselves evolve at larger fields. The vortex lattice is aligned with the 〈1 0 0〉 direction and its rhombic cell apex angle β increases from 64° at 180 Oe to 75–90° at 1000 Oe.