Magnetic, magnetoresistive and structural properties of Cox(CoO)100-x thin film composites

• Published in: Journal of magnetism and magnetic materials Vol. 587; p. 171154
• Main Authors: Sitnikov, A.V., Makagonov, V.A., Kalinin, Y.E., Kushchev, S.B., Foshin, V.A., Perova, N.N., Ganshina, E.A., Granovsky, A.B.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-12-2023
• Subjects: Magnetic properties; Magnetoresistance; Nanocomposite; Magnetoresistance; Nanocomposite; Magnetic properties
• ISSN: 0304-8853
• DOI: 10.1016/j.jmmm.2023.171154

•Heterogeneous Cox(CoO)100-x thin films has been synthesized by ion-beam sputtering of a compound target.•The percolation threshold was significantly lower than that for most of the studied previously nanocomposites.•For compositions near the percolation threshold, a negative tunnel-type magnetoresistance is observed on the dielectric side.•The magnetoresistance is proportional to the square of magnetization and is characterized by hysteresis, which correlates well with magnetic hysteresis.
The structural, magnetic, and magnetoresistive properties of Cox(CoO)100-x thin film composites synthesized by ion-beam sputtering of a composite target in an argon and mixed atmosphere (argon + oxygen) has been studied. The experimentally determined percolation threshold was significantly lower than that for most of the studied previously nanocomposites: ∼ 12.2 at % Co and ∼8.3 at % Co for films fabricated in inert and mixed atmosphere, respectively. This is explained by the special morphology of the films when small metallic Co nanoparticles are located on the surface of larger CoO particles. A negative tunnel-type magnetoresistance reaching 2.4% in 9 kOe field at room temperature was found for composites with close to the percolation threshold Co content. The magnetoresistance is proportional to the square of magnetization and is characterized by hysteresis, which correlates well with magnetic hysteresis. Magnetic hysteresis with a coercivity of the order of 700 Oe is observed for dielectric compositions up to 4 at. % Co. A possible reason for this behavior, along with the special morphology, is the appearance of thin layers of antiferromagnetic oxide at the interface between Co nanoparticles and CoO particles, which causes a significant increase in magnetic anisotropy.