Magnetic Coupling in La_(0.67) Ca_(0.33) MnO_3/La_(0.67) Sr_(0.33) CoO_3/La_(0.67) MnO_3 Trilayer Films

摘要

The perovskite La_(0.67) Ca_(0.33) MnO_3/La_(0.67) Sr_(0.33) CoO_3/La_(0.67) Ca~(0.33) MnO_3 trilayers were fabricated by a facing-target sputtering technique and their magnetotransport properties were investigated. The magnetoresistance is dependent on spacer thickness and dramatically decreases when La_(0.67) Sr_(0.33) CoO_3 layer is thick enough because of its short-circuiting effect. Different from La_(0.67) Ca_(0.33) MnO_3 single layer, trilayer films with thin La_(0.67) Sr_(0.33) CoO_3 spacer have the enhanced metal-semiconductor transition temperature (T_(MS)) of La_(0.67) Ca_(0.33) MnO_3 layers. The magnetic co-ercivity H_C shows a nonmonotonic behavior with changing the spacer layer thickness at 230 K. The waist-like hysteresis indicates that there is an indirect exchange coupling between the top and bottom La_(0.67) Ca~(0.33) MnO_3 layers across the spacer La_(0.67) Sr_(0.33) CoO_3 layer.