Oscillatory magnetoresistance in La 0.67Ca 0.33MnO 3/YBa 2Cu 4O 8/La 0.67Ca 0.33MnO 3 sandwiches

Abstract

Transport properties of La 0.67Ca 0.33MnO 3 (LCMO)/YBa 2Cu 4O 8 (YBCO)/LCMO sandwiches were studied. An oscillatory resistance occurs with a period 30 nm in the series of LCMO (50 nm)/YBCO/LCMO (50 nm) films when the thickness of the YBCO layer is less than 60 nm. In contrast to that for LCMO films, the metal–semiconductor transition temperature for LCMO/YBCO/LCMO films is enhanced and strongly depends on the thickness of the YBCO layer. The magnetoresistance ratio also shows a non-monotonic behavior and a long oscillatory period (80 nm) is found for LCMO (100 nm)/YBCO/LCMO (100 nm) films. These results imply that the magnetic spin interaction between the two LCMO layers may exist through the normal–conductive YBCO layer.