Electronic phase separation in -layers: Usable as a tunneling barrier?

I. Physikalisches Institut, Universität Göttingen - Friedrich-Hund Platz 1 D-37077 Göttingen, Germany

Received: 28 February 2006
Accepted: 16 August 2006

Abstract

Thin -layers were prepared by DC-magnetron sputtering. The structural, magnetic and electronic properties can be tailored by varying the preparation parameters. By reducing the oxygen excess δ within , the lattice constant as well as the activation energy enlarges representing the semiconducting behavior. Beneath a reduced magnetic moment, the -layers seem to show spinglass behavior and an exchange bias field with decreasing δ. This exchange bias is attributed to an exchange interaction between ferromagnetic clusters and the antiferromagnetic matrix. The different areas might be due to electronic phase separation. In order to realize full-oxide, all-manganite tunneling junctions, it was attempted to prepare high-quality /-multilayers, which showed indeed a high quality of stacking with smooth interfaces and without significant Ca diffusion. Tunneling experiments with -barriers and Au and Ir electrodes were successfully performed at low temperatures. Tunneling was observed up to barrier thicknesses of and junction areas of around . The result could be explained in that respect that the ferromagnetic clusters might represent localized states required for inelastic multi-step tunneling.