From Fe${}_3$O${}_4$/NiO bilayers to NiFe${}_2$O${}_4$-like thin films through Ni interdiffusion

Abstract

Ferrites with (inverse) spinel structure display a large variety of electronic and magnetic properties making some of them interesting for potential applications in spintronics. We investigate the thermally induced interdiffusion of Ni${}^{2+}$ ions out of NiO into Fe${}_3$O${}_4$ ultrathin films resulting in off-stoichiometric nickelferrite-like thin layers. We synthesized epitaxial Fe${}_3$O${}_4$/NiO bilayers on Nb-doped SrTiO${}_3$(001) substrates by means of reactive molecular beam epitaxy. Subsequently, we performed an annealing cycle comprising three steps at temperatures of 400\,${}^{\circ }$C, 600\,${}^{\circ }$C, and 800\,${}^{\circ }$C under an oxygen background atmosphere. We studied the changes of the chemical and electronic properties as result of each annealing step with help of hard x-ray photoelectron spectroscopy and found a rather homogenous distribution of Ni and Fe cations throughout the entire film after the overall annealing cycle. For one sample we observed a cationic distribution close to that of the spinel ferrite NiFe${}_2$O${}_4$. Further evidence comes from low energy electron diffraction patterns indicating a spinel type structure at the surface after annealing. Site and element specific hysteresis loops performed by x-ray magnetic circular dichroism uncovered the antiferrimagnetic alignment between the octahedral coordinated Ni${}^{2+}$ and Fe${}^{3+}$ ions and the Fe${}^{3+}$ in tetrahedral coordination. We find a quite low coercive field of 0.02\,T, indicating a rather low defect concentration within the thin ferrite films.

arXiv comment9 pages, 8 figures

References in corpus (10)

• Half-metallic ferromagnets: From band structure to many-body effects
• Quantitative study of the spin Hall magnetoresistance in ferromagnetic insulator/normal metal hybrids
• Subsurface Cation Vacancy Stabilization of the Magnetite (001) Surface
• Thermally driven spin and charge currents in thin NiFe2O4/Pt films
• Longitudinal spin Seebeck effect contribution in transverse spin Seebeck effect experiments in Pt/YIG and Pt/NFO
• 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
• Room Temperature In-plane <100> Magnetic Easy Axis for Fe3O4/SrTiO3(001):Nb Grown by Infrared PLD
• Sign change in the tunnel magnetoresistance of Fe3O4/MgO/Co-Fe-B magnetic tunnel junctions depending on the annealing temperature and the interface treatment
• Structure and morphology of epitaxially grown Fe3O4/NiO bilayers on MgO(001)

Cited by in corpus (6)

• Electrical transport and optical band gap of NiFe${}_{\text{2}}$O${}_{\text{x}}$ thin films
• Real-time monitoring of the structure of ultra thin Fe${}_3$O${}_4$ films during growth on Nb-doped SrTiO${}_3$(001)
• Cation- and lattice-site-selective magnetic depth profiles of ultrathin $\mathrm{F}{\mathrm{e}}_3{\mathrm{O}}_4$(001) films
• Time-resolved diffraction and photoelectron spectroscopy investigation of the reactive molecular beam epitaxy of $\mathrm{F}{\mathrm{e}}_3{\mathrm{O}}_4$ ultrathin films
• Impact of strain and morphology on magnetic properties of Fe${}_3$O${}_4$/NiO bilayers grown on Nb:SrTiO${}_3$(001) and MgO(001)
• Structural and magnetic investigation of the interfaces of $\mathrm{F}{\mathrm{e}}_3{\mathrm{O}}_4/MgO(001)$ with and without NiO interlayer