Session G34 - Focus Session: CMR: Thin Films.
FOCUS session, Tuesday morning, March 04
Room 2, Austin Convention Center
There is much interest in the La_xMn_yO_3-d system due to the large variation of magnetic and electronic states made possible by varying x, y and d. There are strong correlations between the magnetic and the atomic structure that can induce an antiferromagnetic-ferromagnetic transition,(T_c) above room temperature. The connection between the magnetic and electronic states and the atomic structure is not well understood. Growth of films on well known substrates provides an ideal way to controllably test the effect of structure and doping on the magnetic and electronic states. We have grown films of varying doping on (100) SrTiO_3 and have studied the structure of the films on multiple length scales by x-ray absorption spectroscopy (Mn K-edge and La L3-Edge), high-resolution XRD and AFM measurements. In addition, bulk magnetization and transport measurements have been performed. We have correlated the structural changes with the changes in the magnetic and electronic states. In all films the moment per manganese is significantly less than the theoretical values suggesting either canting or a large antiferromagnetic component. Local structural measurements suggest that a large portion of the films independent of doping is in a locally distorted state (possibly insulating). MCD measurements will determine the local moments near the surface for comparison with the previously measured values. This work is supported by NSF Career Grant DMR-9733862 and DMR-0209243.