OBSERVATION OF TILT INDUCED ORIENTATIONAL ORDER IN THE MAGNETIC-FLUX LATTICE IN 2H-NBSE2

We report on observations of the magnetic flux lattice in 2H-NbSe2 usi ng the magnetic decoration technique. For low applied magnetic fields and with the field applied parallel to the c axis of the crystal, we f ind a disordered flux lattice with short-ranged positional and orienta tional order. As the tilt angle of the applied magnetic field increase s, we find that the orientational order in the flux lattice grows dram atically. At high tilt angles, we find a hexatic solid with long-range d orientational order but only short-ranged positional order. This is the first observation of a flux lattice in which the orientational ord er is stabilized by changing the tilt angle of the applied magnetic fi eld in an anisotropic superconductor.