Giant Anisotropy of Magnetoresistance and "Spin Valve" effect in Antiferromagnetic $Nd_{2-x}Ce_xCuO_{4}$

Abstract

We have studied anisotropic magnetoresistance (MR) and magnetization with rotating magnetic field (B) within CuO2 plane in lightly doped AF N d2−xCexCuO4. A giant anisotropy in MR is observed at low temperature below 5 K. The c-axis resistivity can be tuned about one order of magnitude just by changing B direction within CuO2 plane and a scaling behavior between outof-plane and in-plane MR is found. A "Spin valve" effect is proposed to understand the giant anisotropy of out-of-plane MR and the evolution of scaling parameters with the external field. It is found that the field-induced spin-flop transition of Nd 3+ layer under high magnetic field is the key to understand the giant anisotropy. These results suggest that a novel entanglement between charge and spin dominates the underlying physics.