Electrical transport and optical band gap of NiFe${}_{\text{2}}$O${}_{\text{x}}$ thin films

Abstract

We fabricated NiFe${}_{\text{2}}$O${}_{\text{x}}$ thin films on MgAl${}_2$O${}_4$(001) substrates by reactive dc magnetron co-sputtering varying the oxygen partial pressure during deposition. The fabrication of a variable material with oxygen deficiency leads to controllable electrical and optical properties which would be beneficial for the investigations of the transport phenomena and would, therefore, promote the use of such materials in spintronic and spin caloritronic applications. We used several characterization techniques in order to investigate the film properties, focusing on their structural, magnetic, electrical, and optical properties. From the electrical resistivity measurements we obtained the conduction mechanisms that govern the systems in high and low temperature regimes, extracting low thermal activation energies which unveil extrinsic transport mechanisms. The thermal activation energy decreases in the less oxidized samples revealing the pronounced contribution of a large amount of electronic states localized in the band gap to the electrical conductivity. Hall effect measurements showed the mixed-type semiconducting character of our films. The optical band gaps were determined via ultraviolet-visible spectroscopy. They follow a similar trend as the thermal activation energy, with lower band gap values in the less oxidized samples.

References in corpus (17)

• Spin Hall effect
• Spin Hall Magnetoresistance Induced by a Non-Equilibrium Proximity Effect
• Theory of spin Hall magnetoresistance
• Quantitative study of the spin Hall magnetoresistance in ferromagnetic insulator/normal metal hybrids
• Observation of the spin Seebeck effect in epitaxial Fe3O4 thin films
• Epitaxial strain effects in the spinel ferrites CoFe2O4 and NiFe2O4 from first principles
• Thermally driven spin and charge currents in thin NiFe2O4/Pt films
• Electronic structure and optical band gap determination of NiFe2O4
• Longitudinal spin Seebeck effect contribution in transverse spin Seebeck effect experiments in Pt/YIG and Pt/NFO
• Static magnetic proximity effect in Pt/NiFe2O4 and Pt/Fe bilayers investigated by x-ray resonant magnetic reflectivity
• Physical characteristics and cation distribution of NiFe2O4 thin films with high resistivity prepared by reactive co-sputtering
• Enhanced ferrimagnetism in auxetic NiFe2O4 in the crossover to the ultrathin film limit
• Nonlocal magnon spin transport in NiFe${}_2$O${}_4$ thin films
• A Robust Approach for the Growth of Epitaxial Spinel Ferrite Films
• From Fe${}_3$O${}_4$/NiO bilayers to NiFe${}_2$O${}_4$-like thin films through Ni interdiffusion
• Static Magnetic Proximity Effect in Pt Layers on Sputter-Deposited NiFe2O4 and on Fe of Various Thicknesses Investigated by XRMR
• Detection of DC currents and resistance measurements in longitudinal spin Seebeck effect experiments on Pt/YIG and Pt/NFO

Cited by in corpus (3)

• Enhancement in Thermally Generated Spin Voltage at Pd/NiFe${}_2$O${}_4$ Interfaces by the Growth on Lattice-Matched Substrates
• Vectorial observation of the spin Seebeck effect in epitaxial NiFe${}_2$O${}_4$ thin films with various magnetic anisotropy contributions
• Investigation of lattice dynamics, magnetism and electronic transport in $\beta$-Na${}_{0.33}$V${}_2$O${}_5$