PRESSURE EFFECT ON THE MAGNETIC ORDER OF GD IN GDBA2CU3O6.3 SINGLE-CRYSTALS

The pressure effect up to 1 GPa on the magnetic T-H diagram of GdBa2Cu 3O6.3 single crystals is studied by means of AC susceptibility measure ments in the temperature range 0.05-4 K. The spin flop (SF) transition observed below 1 K in magnetic fields applied along the C-axis has th e same character as in a 2D antiferromagnet. The SF transition field, H-SF(0) = 13 kOe, is pressure-independent but the SF phase region is e xtended under pressure, due to the increase of the exchange interactio n and the decrease of the anisotropy field, The magnetic behavior unde r pressure is described in the model of a two-sublattice antiferromagn et with anisotropic intralayer exchange interaction and single ion ani sotropy.