Andreev reflection in ferrimagnetic CoFe2O4/SrRuO3 spin filters

TL;DR

This study investigates Andreev reflection in a ferrimagnetic CoFe2O4/SrRuO3 spin filter, revealing a moderate positive spin filtering efficiency influenced by microstructure and symmetry effects.

Contribution

It provides the first measurement of spin filter efficiency in CoFe2O4/SrRuO3 heterostructures using point contact spectroscopy.

Findings

Spin filter efficiency is not larger than +13%.

Moderate positive spin filtering observed.

Microstructure and symmetry effects influence spin filtering.

Abstract

We have performed point contact spectroscopy measurements on a sample constituted by a metallic ferromagnetic oxide (SrRuO_3) bottom electrode and a tunnel ferrimagnetic (CoFe_2O_4) barrier. Andreev reflection is observed across the tunnel barrier. From the comparison of Andreev reflection in SrRuO3 and across the CoFe_2O_4 barrier we infer that the ferrimagnetic barrier has a spin filter efficiency not larger than +13%. The observation of a moderate and positive spin filtering is discussed in the context of the microstructure of the barriers and symmetry-related spin filtering effects.