Magnetic tunnel junctions based on CrO2∕SnO2 epitaxial bilayers

Abstract

Magnetic tunnel junctions were fabricated using thin films of the half-metallic ferromagnet CrO2, employing SnO2 tunnel barriers. Heteroepitaxial CrO2∕SnO2 bilayers were grown on (100)-TiO2 substrates via chemical vapor deposition. X-ray diffraction and transmission electron microscopy confirmed heteroepitaxy. A polycrystalline cobalt film forms the top magnetic electrode, yielding CrO2(001)∕SnO2(001)∕Co structures after patterning. Tunneling magnetoresistances (TMR) up to +14% at 10K were observed. The sign of the TMR reverses for barrier thicknesses <1nm, attributed to tunneling being dominated by Co-3d states at low thicknesses and Co-4s states at larger thicknesses.