Preparation and structural characterization of FeCo epitaxial thin films on insulating single-crystal substrates

Nishiyama, Tsutomu; Ohtake, Mitsuru; Kirino, Fumiyoshi; Futamoto, Masaaki

doi:10.1063/1.3334200

Cited by 9 publications

(10 citation statements)

References 7 publications

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“…The most intense one at 43.0 • corresponds to MgO (200), which completely overlaps with the peak of the NiO (200) plane due to a very close mismatch between both lattices and the peak at 64.2 • corresponding to FeCo (200), which indicates that the complete heterostructure grows in the (100) direction. The lattice parameter for the FeCo layer, 0.290 nm, indicates that the FeCo layer grows 45 • rotated with respect to the NiO (100) layer to reduce the mismatch to −4.6%, in a similar way to the growth of FeCo on MgO (001) substrates [22,23].…”

Section: Resultsmentioning

confidence: 96%

“…Related to the growth of FeCo thin films on MgO (001), it is established that FeCo can grow epitaxially on MgO (001) substrates with a 45 • rotation between the FeCo and MgO crystal lattices [22,23]. Several bilayers with different FeCo thicknesses were fabricated and characterized, structurally and magnetically, by X-ray diffraction (XRD), Rutherford Backscattering Spectrometry (RBS), Raman spectroscopy, and vectorial Kerr magnetometry (v-MOKE).…”

Section: Introductionmentioning

confidence: 99%

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Influence of the Substrate on the Exchange Coupling of NiO/FeCo Bilayers

Lorenzo-Feijoo,

Serrano,

Hernández-Gómez

et al. 2024

Crystals

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Antiferromagnetic/ferromagnetic (AF/F) systems have been extensively investigated due to the importance that interfacial exchange coupling effects have in the development of magnetic storage technologies. Recently, these systems have garnered interest for the potential they have to imprint the magnetic moments of the AF into an F layer, offering the possibility of using it as a read-out mechanism in antiferromagnetic spintronics. In this study, we explored the importance of crystalline orientation and strains induced by the substrate in the exchange coupling properties of NiO/FeCo AF/F bilayers. For that, we have grown NiO/FeCo bilayers on MgO (001) and Al2O3 (0001) substrates varying the FeCo layer thickness. In addition, we have analyzed both deposited samples and those with induced interfacial unidirectional anisotropy. For inducing such interfacial anisotropy, we used a field cooling procedure, heating the bilayers to 650 K and subsequently cooling down to room temperature under the presence of an external magnetic field of 300 mT. We have investigated the effect of the substrate in terms of crystalline orientation and lattice mismatching on the AF/F exchange coupling as well as the dependence of the coercivity and exchange bias on the inverse F layer thickness that is consistent with the interfacial origin of the AF/F exchange coupling. Moreover, the angular dependence of the magnetic properties was explored by using vectorial Kerr magnetometry, confirming the presence of both magnetocrystalline anisotropy, arising from the epitaxial character of the growing process mainly when the bilayer is grown on MgO (001) substrates, and the field cooling (FC)-induced unidirectional anisotropy.

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Section: Resultsmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Influence of the Substrate on the Exchange Coupling of NiO/FeCo Bilayers

Lorenzo-Feijoo,

Serrano,

Hernández-Gómez

et al. 2024

Crystals

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“…Pt (0 0 1), Pd (0 0 1), Rh (0 0 1), Ir (0 0 1), Au-Cu (0 0 1) [7][8][9][10]) and crystal substrates (e.g. MgO (1 0 0) and MgO (1 1 0) [11], MgO (1 1 1) [11,12], SrTiO 3 (1 1 1) and Al 2 O 3 (0 0 0 1) [12], GaAs (0 0 1) [13]). However, this strategy only allows a tetragonal reconstruction of the Fe-Co to be efficiently triggered up to a critical thickness of few nanometers, above which the crystal structure relaxes to the magnetically soft cubic phase [14].…”

Section: Introductionmentioning

confidence: 99%

Coherently strained [Fe–Co(C)/Au–Cu]_n multilayers: a path to induce magnetic anisotropy in Fe–Co films over large thicknesses

Giannopoulos¹,

Salikhov²,

Varvaro³

et al. 2018

J. Phys. D: Appl. Phys.

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Among novel critical-element-free materials for permanent magnets, the nearly equiatomic Fe-Co alloy has recently attracted a great deal of attention as a large magneto-crystalline anisotropy can be induced by straining the Fe-Co unit cell. In thin film systems, the use of a suitable underlayer allows a tetragonal reconstruction of the Fe-Co to be triggered up to a critical thickness of few nanometers, above which the crystal structure relaxes to the magnetically soft cubic phase. Scaling-up the thickness of the metastable tetragonal Fe-Co phase is of crucial significance for different nanoscale applications, such as magnetic micro-and nano-electromechanical systems. To suppress the strain relaxation occurring at high thicknesses, we explored a novel approach based on Fe-Co(C)/Au-Cu multilayer films, where both Au-Cu interlayers and carbon (C) doping were used to stabilize the strained Fe-Co tetragonal phase over large thicknesses. Both doped and un-doped multilayer structures show a coherently strained regime, persisting up to a thickness of 60 nm, which leads, possibly in combination with the surface anisotropy induced at the Au-Cu interfaces, to the appearance of a large out-of-plane anisotropy (up to 0.4 MJ m −3 ), thus suggesting the potential of such an approach to develop critical-element-free thin film permanent magnets for a variety of nanoscale applications.

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“…The crystal symmetry of Fe-Co alloys can be broken by strained epitaxial growth on a suitable buffer layer [13][14][15][16][17]. Due to a lattice mismatch between the Fe 1−x Co x alloys and the buffer a tetragonal distortion of the Fe-Co unit cell can be stabilized, where the long c-axis is aligned perpendicular to the film plane.…”

Section: Introductionmentioning

confidence: 99%

“…Due to a lattice mismatch between the Fe 1−x Co x alloys and the buffer a tetragonal distortion of the Fe-Co unit cell can be stabilized, where the long c-axis is aligned perpendicular to the film plane. The magnitude of the tetragonal distortion (quantified by the c/a ratio of lattice constants) and, accordingly, the resulting MAE can be tuned by selecting an appropriate buffer lattice constant [13][14][15][16][17][18]. An exceptionally large MAE of the order of 1 MJ m −3 has recently been reported for 3 nm Fe-Co films grown on Au 0.5 Cu 0.5 buffer layers [19].…”

Section: Introductionmentioning

confidence: 99%

Enhanced spin–orbit coupling in tetragonally strained Fe–Co–B films

Salikhov

Reichel

Zingsem

et al. 2017

J. Phys.: Condens. Matter

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Tetragonally strained interstitial Fe-Co-B alloys were synthesized as epitaxial films grown on a 20 nm thick AuCu buffer layer. Different ratios of the perpendicular to in-plane lattice constant c/a = 1.013, 1.034 and 1.02 were stabilized by adding interstitial boron with different concentrations 0, 4, and 10 at.%, respectively. Using ferromagnetic resonance (FMR) and x-ray magnetic circular dichroism (XMCD) we found that the total orbital magnetic moment significantly increases with increasing c/a ratio, indicating that reduced crystal symmetry and interstitial B leads to a noticeable enhancement of the effect of spin-orbit coupling (SOC) in the Fe-Co-B alloys. First-principles calculations reveal that the increase in orbital magnetic moment mainly originates from B impurities in octahedral position and the reduced symmetry around B atoms. These findings offer the possibility to enhance SOC phenomena-namely the magnetocrystalline anisotropy and the orbital moment-by stabilizing anisotropic strain by doping 4 at.% B. Results on the influence of B doping on the Fe-Co film microstructure, their coercive field and magnetic relaxation are also presented.

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Preparation and structural characterization of FeCo epitaxial thin films on insulating single-crystal substrates

Cited by 9 publications

References 7 publications

Influence of the Substrate on the Exchange Coupling of NiO/FeCo Bilayers

Influence of the Substrate on the Exchange Coupling of NiO/FeCo Bilayers

Coherently strained [Fe–Co(C)/Au–Cu]_n multilayers: a path to induce magnetic anisotropy in Fe–Co films over large thicknesses

Enhanced spin–orbit coupling in tetragonally strained Fe–Co–B films

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Preparation and structural characterization of FeCo epitaxial thin films on insulating single-crystal substrates

Cited by 9 publications

References 7 publications

Influence of the Substrate on the Exchange Coupling of NiO/FeCo Bilayers

Influence of the Substrate on the Exchange Coupling of NiO/FeCo Bilayers

Coherently strained [Fe–Co(C)/Au–Cu]n multilayers: a path to induce magnetic anisotropy in Fe–Co films over large thicknesses

Enhanced spin–orbit coupling in tetragonally strained Fe–Co–B films

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Coherently strained [Fe–Co(C)/Au–Cu]_n multilayers: a path to induce magnetic anisotropy in Fe–Co films over large thicknesses