Magnetic behavior and role of the antiphase boundaries in Fe3O4 epitaxial films sputtered on MgO (001)

Bobo, Jean-François; Basso, D.; Snoeck, E.; Gatel, Christophe; Hrabovský, D.; Gauffier, J.L.; Ressier, Laurence; Mamy, R.; Višňovský, Š.; Hamrle, Jaroslav; Teillet, J.; Fert, A.

doi:10.1007/s100510170020

Cited by 51 publications

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“…The RHEED patterns ͓Figs. 1͑c͒ and 1͑d͔͒ are similar to those observed 10,11 12 although the large lattice mismatch of 5% probably leads to films of quality inferior to the present case. However, even a lattice mismatch of 1.9% is not expected to yield the sharp and streaky patterns we observe in Figs.…”

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confidence: 86%

High quality Fe3−δO4∕InAs hybrid structure for electrical spin injection

Ferhat

Yoh²

2007

Applied Physics Letters

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Single crystalline Fe 3−␦ O 4 ͑0 ഛ ␦ ഛ 0.33͒ films have been epitaxially grown on InAs ͑001͒ substrates by molecular beam epitaxy using O 2 as source of active oxygen. Under optimum growth conditions, in situ real time reflection high-energy electron diffraction patterns, along with ex situ atomic force microscopy, indicate that ͑001͒ Fe 3−␦ O 4 can be grown under step-flow-growth mode with a characteristic ͑ ͱ 2 ϫ ͱ 2͒R45 surface reconstruction. X-ray photoelectron spectroscopy demonstrates the possibility of obtaining iron oxides with compositions ranging from Fe 3 O 4 to ␥-Fe 2 O 3 . Measurements with a superconducting quantum interference device magnetometer at 300 K show good magnetic properties, suggesting that iron-based oxides may be promising for spintronic applications. © 2007 American Institute of Physics. ͓DOI: 10.1063/1.2713784͔ During the last decade, there has been a considerable increase of studies on hybrid structures combining both semiconductors and magnetic materials. These studies are motivated by possible applications in the nascent field of spintronics, since the electron spin degree of freedom in hybrid structures is believed to be a source of a rich array of new physical phenomena. Different approaches have been adopted for the selection of adequate spin injectors including ferromagnetic metals, 1,2 dilute magnetic semiconductors, 3 and Heusler alloys. 4 The use of magnetic semiconductors in this field presents the formidable task of increasing the Curie temperature. Ferromagnetic metal and Heusler alloys on the other hand suffer from structural and interfacial problems during their growth. Quite surprisingly, there are few reports on iron oxide based half metals, which exhibit a large polarization at the Fermi level making them very attractive for spin injection into semiconductors.Fe 3 O 4 or magnetite belongs to a large family of ironbased oxides commonly called ferrites. Our choice for this material as a possible efficient spin injector into semiconductors stems from its physical properties, which are attractive in many respects. ͑i͒ It has half metallic character with a large spin polarization at the Fermi level. 5,6 ͑ii͒ It possesses an electrical resistivity of the same order of magnitude as a semiconductor, making the conductivity mismatch problem less severe than in the case of metals. ͑iii͒ It has a Curie temperature of about 850 K, well above room temperature. This study will combine the use of magnetite with InAs substrates. InAs is used because of high room temperature electron mobility and, more importantly, because of its large and tunable spin-orbit coupling strength ͑small ratio between the Rashba and Dresselhauss terms͒, important for spin-based devices. 7 Although the growth of iron oxides on metallic and oxide based substrates is a very well documented subject, 8 there are only few reports on the growth of iron oxides on semiconducting substrates.The purpose of the present letter is to extend the only work available 9 on the growth of Fe 3 O 4 on InAs with special emp...

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confidence: 86%

High quality Fe3−δO4∕InAs hybrid structure for electrical spin injection

Ferhat

Yoh²

2007

Applied Physics Letters

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“…MgO has the most intense peak and the thin film peak is shifted by ∆ω ~0.15º with respect to the MgO peak. By adding the ∆ω between the MgO peak and the [4,9], scanning tunnelling microscopy [3] and magnetic force microscopy [9] studies, the exact structure of APBs is not yet clear. The regions around APBs could be stoichiometric or non-stoichiometric as the APBs themselves are metastable defects.…”

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confidence: 99%

“…Strain in epitaxial magnetite films has a strong influence on the magnetic and magneto-transport properties. Though there exist reports on the growth and characterisation of thin films of magnetite on different substrates [3][4][5][6][7][8][9][10][11], the strain relaxation behaviour in Fe 3 O 4 /MgO films grown by sputtering technique has not been investigated in detail. The lattice mismatch between the film and substrate is − 0.344%.…”

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confidence: 99%

Strain relaxation studies of the Fe₃O₄/MgO (100) heteroepitaxial system grown by magnetron sputtering

Balakrishnan

Arora

Shvets³

2004

J. Phys.: Condens. Matter

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PACS numbers:68.55Jk: Structure and morphology; thickness; crystalline orientation and texture 81.15Cd: Deposition by sputtering 75.50Bb: Fe and its alloys Detailed strain relaxation studies on epitaxial magnetite, Fe 3 O 4 , films on MgO (100) substrates grown by magnetron sputtering reveal the accommodation of strain up to 600 nm thickness, a thickness much above the critical thickness (t c ) predicted by theoretical models. The results are in agreement with the suggestion that the excess strain in Fe 3 O 4 /MgO (100) hetero-epitaxy is accommodated by the presence of antiphase boundaries. The compressive strain generated by the antiphase boundaries compensate for the tensile strain within the growth islands, allowing the film to remain fully coherent with the substrate. Contrary to the earlier findings, magnetisation decreases with an increase in film thickness. This vindicates the view that the structure of the antiphase boundaries depend on the growth conditions. Key words: Magnetite; Hetero-epitaxy; Strain relaxation; Magnetron sputtering; Antiphase boundary Introduction Magnetite, Fe 3 O 4 , is one of the transition metal oxides studied most extensively owing to its high Curie temperature (T C ), metal-insulator transition at low temperatures (~120 K) [1] and half-metallic nature [2]. Epitaxial films of magnetite hold out promise for device fabrication. Strain in epitaxial magnetite films has a strong influence on the magnetic and magneto-transport properties. Though there exist reports on the growth and characterisation of thin films of magnetite on different substrates [3][4][5][6][7][8][9][10][11], the strain relaxation behaviour in Fe 3 O 4 /MgO films grown by sputtering technique has not been investigated in detail. The lattice mismatch between the film and substrate is − 0.344%. In our previous study [12] on the strain relaxation behaviour of Fe 3 O 4 /MgO (100) hetero-epitaxial films grown by oxygen assisted molecular beam epitaxy (MBE), it was shown that the films remain in a fully strained state up to a much greater thickness than that predicted (~70 nm) by critical thickness models based on misfit strain [13,14]. The anomalous strain-relaxation behaviour was attributed [12] to the presence of antiphase boundaries (APBs). The APBs are the natural defects occurring during growth in Fe 3 O 4 /MgO hetero-epitaxial system [4,5]. The oxygen atoms in both Fe 3 O 4 and MgO are arranged in a facecentred cubic (fcc) lattice. The lattice constant of Fe 3 O 4 (a=8.3987 Å) is nearly twice that of MgO (a=4.213 Å) due to the specific arrangement of Fe atoms at the vacant interstitial tetrahedral (A) and octahedral (B) sites. During the growth, the islands nucleate randomly and when they coalesce they can be shifted or rotated with respect to each other, forming antiphase boundaries. At some of these boundaries the angle subtended by the cation-anion-cation interaction is 180° and hence the superexchange interaction between the cations mediated by oxygen is antiferromagnetic. This results in a picture where la...

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“…12 The magnetic structures in the presence of APB found so far are irregular. 7,13 In this study we employed epitaxial Fe 3 O 4 films that were subjected to a short mild annealing under ambient conditions ͑250°C, 4 min͒. Such a post-growth annealing only marginally changes the stochiometry of magnetite to Fe 3−␦ O 4 with a value of ␦ Ϸ 0.03± 0.01 as determined from Mössbauer measurements.…”

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Observation of antiferromagnetic coupling in epitaxial ferrite films

Knittel¹,

Wei²,

Yinqing

et al. 2006

Phys. Rev. B

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Magnetic behavior and role of the antiphase boundaries in Fe3O4 epitaxial films sputtered on MgO (001)

Cited by 51 publications

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High quality Fe3−δO4∕InAs hybrid structure for electrical spin injection

High quality Fe3−δO4∕InAs hybrid structure for electrical spin injection

Strain relaxation studies of the Fe₃O₄/MgO (100) heteroepitaxial system grown by magnetron sputtering

Observation of antiferromagnetic coupling in epitaxial ferrite films

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Magnetic behavior and role of the antiphase boundaries in Fe3O4 epitaxial films sputtered on MgO (001)

Cited by 51 publications

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High quality Fe3−δO4∕InAs hybrid structure for electrical spin injection

High quality Fe3−δO4∕InAs hybrid structure for electrical spin injection

Strain relaxation studies of the Fe3O4/MgO (100) heteroepitaxial system grown by magnetron sputtering

Observation of antiferromagnetic coupling in epitaxial ferrite films

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Strain relaxation studies of the Fe₃O₄/MgO (100) heteroepitaxial system grown by magnetron sputtering