Controlling Degree of Inversion in MgFe2O4 Spinel Films Grown in External Magnetic Fields

Abstract

Single‐phase magnesium ferrite spinel films (MgFe2O4) were grown by magnetic field‐assisted chemical vapor deposition (mfCVD) of a mixed‐metal precursor compound, [MgFe2(OtBu)8]. The formation of monophasic MgFe2O4 deposits as a function of the applied magnetic field strength (B = 0.0, 0.5, and 1.0 T) was investigated and confirmed by X‐ray diffraction and photoelectron spectroscopy analyses. Thin film cross‐sectional electron microscopic analysis (FIB‐SEM) exhibited higher grain growth and densification in MgFe2O4 films obtained under the magnetic field influence when compared to spinel samples grown under zero‐field conditions. Application of an external magnetic field of varying strengths during the chemical vapor deposition process resulted in a change in the light absorption properties and crystal orientation in the MgFe2O4 films, evident in the decreased photoabsorbance analyzed by the UV‐Vis spectra and the decrease of intensity of the (400) peak in MgFe2O4 films grown under magnetic field. A comprehensive analysis of X‐ray diffraction and X‐ray magnetic circular dichroism (XMCD) results indicated a higher degree of inversion in MgFe2O4 deposits grown in an external magnetic field corroborated by a larger contribution of ligand field transitions of tetrahedrally coordinated Fe(III) centers affecting the visible light absorption of MgFe2O4 films.