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Structural transformations and interfacial iron reduction in heterostructures with epitaxial layers of 3 d metals and ferrimagnetic oxides
Author(s) -
Suturin Sergey,
Kaveev Andrey,
Korovin Aleksandr,
Fedorov Vladimir,
Sawada Masahiro,
Sokolov Nikolai
Publication year - 2018
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s1600576718007823
Subject(s) - materials science , ferrimagnetism , ferromagnetism , electron diffraction , antiferromagnetism , oxide , low energy electron diffraction , heterojunction , epitaxy , metal , crystallography , iron oxide , transition metal , crystal structure , diffraction , chemical physics , condensed matter physics , nanotechnology , magnetization , layer (electronics) , chemistry , metallurgy , optics , magnetic field , optoelectronics , biochemistry , physics , quantum mechanics , catalysis
The present paper sheds light on the interfacial structural transformation taking place upon epitaxial growth of ferromagnetic 3 d metal compounds – Co, Ni and CoFeB – on the surface of magnetically ordered iron oxides – Fe 3 O 4 , Fe 2 O 3 and Y 3 Fe 5 O 12 . The reducing conditions due to the excess of neutral metal atoms at the surface cause reduction of the Fe 3+ ions of the underlying iron oxide layer to the Fe 2+ state and subsequent recrystallization of the subsurface region to an MeO‐like rock salt crystal structure. The corresponding change of the lattice symmetry can be readily recognized by in situ high‐energy electron diffraction reciprocal‐space mapping and ex situ X‐ray diffraction techniques. From an analysis of diffraction and X‐ray absorption data a tentative model of the structural transformation is proposed, based on penetration of Me atoms into the near‐surface region of the iron oxide lattice. Once a few nanometre thick oxidized layer is formed, further growth of pure metallic film with native crystal structure takes place. An important observation made is that the oxidation/reduction effects do not occur when 3 d metals are deposited onto more stable MgO and Gd 3 Ga 5 O 12 surfaces. This circumstance makes it appropriate to propose these materials for use as buffer layers to prevent formation of antiferromagnetic monoxide transition regions in multilayered magnetic structures. The presented results are supposed valuable for development of hybrid ferromagnetic heterostructures attractive for various spintronic applications.