Thickness dependence of magnetic and magneto-transport properties of polycrystalline Fe3O4 films prepared by reactive sputtering at room temperature

• Published in: Journal of physics. D, Applied physics Applied physics, 2003-12, Vol.36 (23), p.2950-2953
• Main Authors: Liu, Hui, Jiang, E Y, Bai, H L, Zheng, R K, Zhang, X X
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Electronic transport in mesoscopic or nanoscale materials and structures; Electronic transport in multilayers, nanoscale materials and structures; Exact sciences and technology; Magnetic properties and materials; Magnetic properties of monolayers and thin films; Magnetic properties of nanostructures; Magnetic properties of surface, thin films and multilayers; Physics
• ISSN: 0022-3727; 1361-6463
• DOI: 10.1088/0022-3727/36/23/013

At room temperature, polycrystalline Fe3O4 films with thicknesses in the range 5-1120 nm have been prepared by reactive sputtering. Transmission electron microscopy imaging shows that uniform Fe3O4 grains are well separated by grain boundaries and their size decreases with film thickness. The change of resistivity as a function of temperature reveals a grain boundary dominated electron tunnelling mechanism. The magnetoresistance MR = (*rH - *r0po)*r0 measured at room temperature for the films thicker than 200 nm is ~-7.4% under a magnetic field of 46 kOe, which is among the largest values ever reported for Fe3O4 films under the same measuring conditions. As the thickness reduces from 80 to 5 nm, MR decreases from -6.5% to -1.1% due to the enhanced spin-flip scattering at film and grain surfaces.