Perpendicular Magnetic Anisotropy Induced by Tetragonal Distortion of FeCo Alloy Films Grown on Pd(001)

Winkelmann, Aimo; Przybylski, M.; Luo, Feng; Shi, Yong; Barthel, J.

doi:10.1103/physrevlett.96.257205

Cited by 94 publications

(82 citation statements)

References 12 publications

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“…Until now, large MAE values have been predicted and experimentally observed only in distorted FeCo-bct bulk, respectively, several monolayers thick films. [5][6][7] In a combined experimental and theoretical study we demonstrate that 1-ML-thick Fe x Co 1−x films grown on Pt͑111͒ possess both very large M S and MAE values compared to most ferromagnetic materials.…”

Section: Introductionmentioning

confidence: 99%

“…Bimetallic alloys represent a viable route to tune both M S and the MAE, as these quantities are strongly influenced by compositional effects and lattice distortions. While the MAE of ferromagnetic transition metals in their cubic structures is on the order of a few tens of eV/ atom, structurally distorted alloys, such as FePt in the L1 0 phase [2][3][4] or bct-FeCo, [5][6][7] may have MAE values close to 1 meV/atom. Moreover, the total magnetic moment can be tuned by choosing the two elements of the alloy.…”

Section: Introductionmentioning

confidence: 99%

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High magnetic moments and anisotropies forFexCo1−xmonolayers on Pt(111)

et al. 2008

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The magnetism of 1-ML-thick films of Fe x Co 1−x on Pt͑111͒ was investigated both experimentally, by x-ray magnetic circular dichroism and magneto-optical Kerr effect measurements, and theoretically, by firstprinciples electronic structure calculations, as a function of the film chemical composition. The calculated Fe and Co spin moments are only weakly dependent on the composition and close to 3 B / atom and 2 B / atom, respectively. This trend is also seen in the experimental data, except for pure Fe, where an effective spin moment of only S eff = ͑1.2Ϯ 0.2͒ B / atom was measured. On the other hand, both the orbital moment and the magnetic anisotropy energy show a strong composition dependence with maxima close to the Fe 0.5 Co 0.5 stoichiometry. The experiment, in agreement with theory, gives a maximum magnetic anisotropy energy of 0.5 meV/atom, which is more than 2 orders of magnitude larger than the value observed in bulk bcc FeCo and close to that observed for the L1 0 phase of FePt. The calculations clearly demonstrate that this composition dependence is the result of a fine tuning in the occupation number of the d x 2 −y 2 and d xy orbitals due to the Fe-Co electronic hybridization.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

High magnetic moments and anisotropies forFexCo1−xmonolayers on Pt(111)

et al. 2008

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“…Calculations 2,3 based on Density Functional Theory (DFT) predicted remarkably high MCAs if the unit cell would be tetragonally distorted with c/a between 1.2 and 1.25. The most common approach to strain the unit cell experimentally [8][9][10][11] is coherent epitaxial growth of thin films on suitable substrates that provide appropriate in-plane lattice parameters a. Assuming constant volume of the Fe-Co unit cell, a strain parallel to the film normal is expected when a is smaller than the equilibrium lattice parameter of Fe-Co. Up to now, tetragonally distorted Fe-Co films with perpendicular easy axis of magnetization could not be produced with film thicknesses exceeding 15 monolayers (ML) [9][10][11] .…”

Section: Introductionmentioning

confidence: 99%

Increased magnetocrystalline anisotropy in epitaxial Fe-Co-C thin films with spontaneous strain

Reichel

Giannopoulos

Kauffmann-Weiss

et al. 2014

Journal of Applied Physics

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Rare earth free alloys are in focus of permanent magnet research since the accessibility of the elements needed for nowadays conventional magnets is limited. Tetragonally strained iron-cobalt (Fe-Co) has attracted large interest as promising candidate due to theoretical calculations. In experiments, however, the applied strain quickly relaxes with increasing film thickness and hampers stabilization of a strong magnetocrystalline anisotropy. In our study we show that already 2 at% of carbon substantially reduce the lattice relaxation leading to the formation of a spontaneously strained phase with 3 % tetragonal distortion. In these strained (Fe 0.4 Co 0.6 ) 0.98 C 0.02 films, a magnetocrystalline anisotropy above 0.4 MJ/m 3 is observed while the large polarization of 2.1 T is maintained. Compared to binary Fe-Co this is a remarkable improvement of the intrinsic magnetic properties. In this paper, we relate our experimental work to theoretical studies of strained Fe-Co-C and find a very good agreement.

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“…These observations were frequently made at distinct dimensionalities as pseudomorphically grown single layer films [12,13], multilayer thin films [14] as well as nanocrystalline films [15]. However, the lattice constants of equiatomic (pseudo-)fcc FeCo (a FeCo = 0.354 nm [11]) and TiN (a TiN = 0.424 nm [16]) would yield a relative lattice mismatch of ((a TiN −a FeCo )/a TiN = 0.165).…”

Section: Discussionmentioning

confidence: 99%

Epitaxially stabilized TiN/(Ti,Fe,Co)N multilayer thin films in (pseudo-)fcc crystal structure by sequential magnetron sputter deposition

Klever¹,

Seemann²,

Stüber³

et al. 2010

J. Phys. D: Appl. Phys.

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Abstract. Multilayer thin films were grown by non-reactive sequential magnetron sputter deposition from ceramic TiN and metallic FeCo targets addressing a combination of wear resistance and sensoric functionality. Coatings with bilayer period values ranging from 449 nm down to 2.6 nm were grown with the total amount of either material maintained constant. The multilayer thin films were post-annealed ex-situ at 600 C for 60 min in vacuum.X-ray diffraction results imply the multilayer thin films to undergo significant changes in its crystalline structure when the bilayer period is decreased. By using high resolution transmission electron microscopy as well as selected area electron diffraction it is shown that in case of multilayer thin films with bilayer periods of several ten nanometers and higher FeCo layers and TiN layers in their respective common CsCl and NaCl type crystal structures alternate. In contrast, in the multilayer thin films with bilayer periods of only a few nanometers, grain growth across the interfaces between the individual layers takes place and a strongly textured microstructure is formed which features columns in pseudo-fcc crystal structure grown in heteroeptaxial growth mode.It is suggested that the experimental findings imply the latter multilayer thin films to be alternately composed of TiN layers and (Ti,Fe,Co)N solid solution layers which have been formed by solid state reaction during the deposition process. As the consequence, epitaxially stabilised columnar grains in strongly textured pseudo-fcc structure are formed. This structure is preserved after the annealing procedure which qualifies these coatings for use in applications where temperatures of up to 600 C are reached.Confidential: not for distribution.

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Perpendicular Magnetic Anisotropy Induced by Tetragonal Distortion of FeCo Alloy Films Grown on Pd(001)

Cited by 94 publications

References 12 publications

High magnetic moments and anisotropies forFexCo1−xmonolayers on Pt(111)

High magnetic moments and anisotropies forFexCo1−xmonolayers on Pt(111)

Increased magnetocrystalline anisotropy in epitaxial Fe-Co-C thin films with spontaneous strain

Epitaxially stabilized TiN/(Ti,Fe,Co)N multilayer thin films in (pseudo-)fcc crystal structure by sequential magnetron sputter deposition

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