Interface assisted high magnetoresistance in BiFeO3/Fe97Si3 thin film at room temperature.

Bilayer thin films of multiferroic oxide BiFeO 3 and metallic alloy Fe 97 Si 3 deposited by RF-magnetron sputtering have been investigated to understand spin polarized electron transport across bilayer interface. Effect of BiFeO 3 thickness variation on magnetic and magnetotransport properties of bilayer thin films has been analyzed. An induced unidirectional magnetic anisotropy in bilayer thin films has been observed by interface coupling between antiferromagnetic BiFeO 3 and ferromagnetic Fe 97 Si 3 spin magnetic moments. Increasing interface roughness with increase in BiFeO 3 film thickness has been found to be a regulatory factor for inducing in-plane unidirectional anisotropy and exchange interaction at bilayer interface. A high magnetic moment ∼315 emu/cc originated at room temperature by uncompensated interface spin density has been measured in 30 nm thick BiFeO 3 film. Magnetic inhomogeneities at interface give rise to a spin glass like phase responsible for spin flip scattering at bilayer interface. Enhanced low field magnetoresistance ∼30% in 60 nm thick BiFeO 3 film is ascribed to intensified scattering from disordered interface states with increasing BiFeO 3 thickness. Magnetodielectric measurements (applied magnetic field 1 kOe) have revealed five times increase in relaxation time of charge carriers inside grains confirming intergrain charge transport dominated by alignment of magnetic moments of nearby grains via exchange coupling. High value of magnetoresistance ∼46% in 60 nm thick film of increased grain size is due to enhanced critical length for charge transport. Observed room temperature magnetoresistive properties of BiFeO 3 /Fe 97 Si 3 thin films are critical for developing multiferroic antiferromagnetic based spintronic devices. Image 1 • High value of room temperature magnetoresistance ∼46% obtained in 60 nm thick BiFeO 3 is significant to develop AFM based spin filters. • Interface roughness was found a key factor to determine magntoresistive and magnetic properties of BiFeO 3 /Fe 97 Si 3 bilayer. • Soft magnetic alloy Fe 97 Si 3 has been integrated with Bismuth Ferrite for the first time to raise its magnetoresistance values by introducing Si scattering centers. • A significant increase in both high field magnetoresistance (HFMR) ∼ 46% and low field magnetoresistance (LFMR) ∼ 30% has been obtained at room temperature. • The above study is also important to develop multiferroic tunnel junctions and sensors functional at room temperature. [ABSTRACT FROM AUTHOR]