Publication

Journal	Physical Review Materials
Volume (Issue)	3(9)
Page(s)	094401 - 094401
Title of proceedings	Physical Review Materials
DOI	10.1103/physrevmaterials.3.094401

URL	http://doi.org/10.1103/PhysRevMaterials.3.094401
Type of Open Access	Publisher (Gold Open Access)

In the present study we have demonstrated epitaxial stabilization of the metastable magnetically hard ɛ−Fe2O3 phase on top of a thin MgO(111) buffer layer grown onto the GaN (0001) surface. The primary purpose to introduce a 4-nm-thick buffer layer of MgO in between Fe2O3 and GaN was to stop thermal migration of Ga into the iron oxide layer. Though such migration and successive formation of the orthorhombic GaFeO3 was supposed earlier to be a potential trigger of the nucleation of the isostructural ɛ−Fe2O3, the present work demonstrates that the growth of single crystalline uniform films of epsilon ferrite by pulsed laser deposition is possible even on the MgO capped GaN. The structural properties of the 60-nm-thick Fe2O3 layer on MgO/GaN were probed by electron and x-ray diffraction, both suggesting that the growth of ɛ−Fe2O3 is preceded by formation of a thin layer of γ−Fe2O3. The presence of the magnetically hard epsilon ferrite was independently confirmed by temperature dependent magnetometry measurements. The depth-resolved x-ray and polarized neutron reflectometry reveal that the 10 nm iron oxide layer at the interface has a lower density and a higher magnetization than the main volume of the ɛ−Fe2O3 film. The density and magnetic moment depth profiles derived from fitting the reflectometry data are in a good agreement with the presence of the magnetically degraded γ−Fe2O3 transition layer between MgO and ɛ−Fe2O3. The natural occurrence of the interface between magnetoelectric ɛ- and spin caloritronic γ-iron oxide phases can enable further opportunities to design novel all-oxide-on-semiconductor devices.