Interaction between magnetism and superconductivity in $La_{0.7}Ca_{0.3}MnO_3$/$YBa_2Cu_3O_{7-\delta}$ multilayers

Angular dependent resistivity measurements were performed on $La_{0.7}Ca_{0.3}MnO_3$/$YBa_2Cu_3O_{7-\delta}$ (LCMO/YBCO) heterostructures below and above the superconducting transition temperature $T_c \approx$ 90 K in different applied magnetic field. Besides the conventional intrinsic anisotropic magnetoresistance (AMR) present above $T_c$, we observe another anisotropic magnetoresistance, which only arises below $T_c$ and increases significantly with decreasing temperature. Also, the proximity-induced resistance, which appears in the LCMO layer, displays a spectacular increase at $T_c$ and then decreases significantly with decreasing temperature, persisting down to the lowest measured T of 72 K. This anomalous AMR and the proximity-induced resistance in the LCMO layer could be due to the triplet component of the superconducting condensation which penetrates into the ferromagnet over a long distance.