MAGNETORESISTANCE AND THE SPIN FLOP TRANSITION IN PURE SINGLE - CRYSTAL LA2CUO4+Y

Magnetoresistance (MR) measurements are reported for pure single crystals of La2CuO4+y at magnetic fields up to 23T. With the magnetic field, parallel to the staggered moment, the MR shows evidence of a spin flop transition, which provides a measure of both the antisymmetric and the symmetric anisotropies of the nearest-neighbour exchange. The MR, which arises from the interlayer hopping conductivity, is proportional to the order parameter of the antiferromagnetism.