Interface-driven magnetoelectric effects in granular CrO₂

¹ Leibniz-Institute for Solid State and Materials Research, IFW Dresden - 01171 Dresden, Germany, EU
² Angewandte Physik, Universität Duisburg-Essen - 47048 Duisburg, Germany, EU
³ Kirchhoff-Institute for Physics, Universität Heidelberg - 69120 Heidelberg, Germany, EU

Received: 15 February 2010
Accepted: 1 July 2010

Abstract

Antiferromagnetic and magnetoelectric Cr₂O₃ surfaces strongly affect the electronic properties in half-metallic CrO₂. We show the presence of a Cr₂O₃ surface layer on CrO₂ grains by high-resolution transmission electron microscopy. The effect of these surface layers is demonstrated by measurements of the temperature variation of the magnetoelectric susceptibility. A major observation is a sign change at about 100 K followed by a monotonic rise as a function of temperature. These electric-field–induced moments in CrO₂ are correlated with the magnetoelectric susceptibility of pure Cr₂O₃. This study indicates that it is important to take into account the magnetoelectric character of thin surface layers of Cr₂O₃ in granular CrO₂ for better understanding the transport mechanism in this system. The observation of a finite magnetoelectric susceptibility near room temperature may find utility in device applications.