Tuning the perpendicular magnetic anisotropy in tetragonally distorted FexCo1−x alloy films on Rh (001) by varying the alloy composition

Luo, Feng; Fu, Xinwen; Winkelmann, Aimo; Przybylski, M.

doi:10.1063/1.2821370

Cited by 59 publications

(56 citation statements)

References 12 publications

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“…These confirmations should be viewed with caution, since in all quantified cases the measured values of K u seem to be lower than the predictions for comparable parameter values of c/a and of x by factors of two to four. In detail, K u ¼ 108 meV per atom was found for Fe 0.5 Co 0.5 jPd(001) films with 3-10 ML thickness, about half the predicted value [10]; for [Fe 0.36 Co 0.64 jPt(001)] n superlattices, only one half [9] or one quarter [11] of the theoretical value was measured, depending on the way of comparison (dedicated calculation for a certain superlattice [9] or evaluation of bulk data from various superlattice data [11]). One should note that in the latter case the anisotropy was measured at room temperature, which explains a part of the discrepancy.…”

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confidence: 92%

The effect of chemical disorder on the magnetic anisotropy of strained Fe–Co films

Neise

Schönecker

Richter

et al. 2011

Physica Status Solidi (b)

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Strained Fe-Co films have recently been demonstrated to exhibit a large magnetocrystalline anisotropy (MCA) and thus to be of potential interest as magnetic storage material. Here, we show by means of density-functional (DF) calculations, that chemical order can remarkably enhance the MCA. We also investigate the effect of relaxation perpendicular to the applied strain and evaluate the strain energy as a function of Co concentration and substrate lattice parameter. On this basis, favourable preparation routes for films with a large perpendicular anisotropy are suggested.

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confidence: 92%

The effect of chemical disorder on the magnetic anisotropy of strained Fe–Co films

Neise

Schönecker

Richter

et al. 2011

Physica Status Solidi (b)

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“…The large values of K u and M s in these alloys were first predicted by first-principles calculations 7 and then confirmed by experiments. [8][9][10][11] In particular, Yildiz et al…”

Section: -4mentioning

confidence: 99%

“…The large values of K u and M s in these alloys were first predicted by first-principles calculations 7 and then confirmed by experiments. [8][9][10][11] In particular, Yildiz et al11 achieved a strong perpendicular magnetic anisotropy (PMA) in tetragonal FeCo alloys epitaxially grown on Pd (c/a = 1.13), Ir (c/a = 1.18), and Rh (c/a = 1.24) substrates. The authors found that the PMA is very sensitive to the tetragonal distortion and increases with increasing c/a ratio, which allows to tune the PMA by growing the alloys on different substrates.…”

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confidence: 99%

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Strong magnon softening in tetragonal FeCo compounds

2013

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Magnons play an important role in fast precessional magnetization reversal processes serving as a heat bath for dissipation of the Zeeman energy and thus being responsible for the relaxation of magnetization. Employing ab initio many-body perturbation theory we studied the magnon spectra of the tetragonal FeCo compounds considering three different experimental c/a ratios, c/a = 1.13, 1.18, and 1.24 corresponding to FeCo grown on Pd, Ir, and Rh, respectively. We find that for all three cases the short-wavelength magnons are strongly damped and tetragonal distortion gives rise to a significant magnon softening. The magnon stiffness constant D decreases almost by a factor of 2 from FeCo/Pd to FeCo/Rh. The combination of soft magnons together with the giant magnetic anisotropy energy suggests FeCo/Rh to be a promising material for perpendicular magnetic recording applications. Since the introduction of the first commercial hard disk drive in 1956, the recording density in a hard disk, that is, the amount of information that can be stored per square inch, has increased by more than seven orders of magnitude to meet an ever-growing need.1 This has been achieved by a simple scaling of the dimensions of the bits recorded in storage medium. Due to the superparamagnetic effect, however, the recording density has an upper limit. For longitudinal magnetic recording it is around 200 Gbit per square inch, whereas it is predicted to be much larger for perpendicular recording, up to 1000 Gbit per square inch, though this limit is constantly changing with the discovery of new materials. 2-4The major problem in designing magnetic storage media is to retain the magnetization of the medium over a long period of time despite thermal fluctuations. If the ratio of the thermal energy k B T to the magnetic energy per grain K u V , where V is the grain volume and K u is the uniaxial magnetocrystalline anisotropy energy (MAE), becomes sufficiently large, the thermal fluctuations can reverse the magnetization in a region of the medium, destroying the data stored there. 3,5 In order to further increase the recording density in future recording media, high-K u materials are needed. 6 Additionally, a large saturation magnetization M s is beneficial to reduce the write field, which has to be applied by the writing head. Materials that combine the desired large values of K u and M s are tetragonal near-equiatomic FeCo alloys. The large values of K u and M s in these alloys were first predicted by first-principles calculations 7 and then confirmed by experiments. [8][9][10][11] In particular, Yildiz et al.11 achieved a strong perpendicular magnetic anisotropy (PMA) in tetragonal FeCo alloys epitaxially grown on Pd (c/a = 1.13), Ir (c/a = 1.18), and Rh (c/a = 1.24) substrates. The authors found that the PMA is very sensitive to the tetragonal distortion and increases with increasing c/a ratio, which allows to tune the PMA by growing the alloys on different substrates.Besides large K u and M s values, another very important issue in magnetic recor...

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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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Tuning the perpendicular magnetic anisotropy in tetragonally distorted FexCo1−x alloy films on Rh (001) by varying the alloy composition

Cited by 59 publications

References 12 publications

The effect of chemical disorder on the magnetic anisotropy of strained Fe–Co films

The effect of chemical disorder on the magnetic anisotropy of strained Fe–Co films

Strong magnon softening in tetragonal FeCo compounds

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

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