Oscillatory magnetoresistance in La0.67Ca0.33MnO3/YBa2Cu4O8/La0.67Ca0.33MnO3 sandwiches

摘要

Transport properties of La0.67Ca0.33MnO3 (LCMO)/YBa2Cu4O8 (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. (C) 2004 Elsevier B.V. All rights reserved.