Cuprate-Manganite Interfaces-What Controls the Properties of FM/SC Oxide Superlattices?

Abstract

Format

This is a copy of the slides presented at the meeting but not formally written up for the volume.

Abstract

The physical properties of complex oxides are characterized by the interplay of charge-,spin-,orbital and lattice degrees of freedom. Combining oxides with different spin-,charge- or orbital order opens generate an additional degree of freedom that can give rise to novel physical phenomena. We have studied the interface of the system La0.67.Ca.33MnO3 and YBa2Cu3O7 prepared by conventional PLD as an example representing the combination of ferromagnetic and superconducting oxides by a variety of techniques including neutron diffraction and XMCD analysis. It turns out that at the interface interaction effects are taking place at two different length scales. One is based on the self ? injection of spin-polarized quasiparticles with a length scale of ~ 10nm, the other is a short range exchange interaction with a length scale of ~ 3 nm. The short range interaction gives rise to an antiferromagnetic coupling of the Mn and Cu spins across the interface. The results are discussed in the frame of orbital interactions across the interface. Furthermore, it could be shown that in FM/SC/FM trilayer systems a so far unknown coupling of adjacent magnetic layers occurs when the superlattices are cooled through the superconducting transition temperature. It is well established that two ferromagnetic layers are coupled through an intervening metallic layer by the Ruddermann-Kittel-Kasuya-Yoshida (RKKY) mechanism. The sign of the coupling oscillates from positive to negative with the thickness of the metallic layer. On the other hand, the interaction between ferromagnetic (FM) and superconducting (SC) layers in a FM/SC/FM heterostructure is not well understood. Tentatively, we propose a coupling mechanism mediated by London screening currents to explain our observations.