Erratum: Calculation of uniaxial magnetic anisotropy energy of tetragonal and trigonal Fe, Co, and Ni [Phys. Rev. B<b>69</b>, 104426 (2004)]

Burkert, Till; Eriksson, Olle; James, P.; Simak, Sergei I.; Johansson, Börje; Nordström, Lars

doi:10.1103/physrevb.70.139901

Cited by 24 publications

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“…With increasing c/a ratio, the anisotropy energy decreases to relatively small negative values. This calculated spin re-orientation transition is consistent with previous DFT calculations, 18 where the effects of tetragonal distortions on pure bct strained Fe were studied. Surprisingly, as the experiments tell us, the interstitial element N-so far neglected-seems to play a decisive role in determining the magnetic anisotropy.…”

Section: -13supporting

confidence: 79%

“…They even lead to a sign change of magneto-crystalline anisotropy corresponding to an easy axis re-orientation from [001] to [100] when the ratio of out-of-plane to in-plane lattice constant becomes larger than c/a ≈ 1.07. 18 Moreover, in the case of the related compound bct α ′ -Fe 8 C, K u is even negative, and the easy axis of magnetization lies in the (001) plane. 6 While first believed to be necessary just for the induction of suited distortions, the individual interstitial elements seem to have much more influence on the magnetic properties-in the above a Electronic mail: hzhang@tmm.tu-darmstadt.…”

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confidence: 99%

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Engineering perpendicular magnetic anisotropy in Fe via interstitial nitrogenation: N choose K

et al. 2016

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In this work, combining experimental results and first principles calculations, we show that interstitial nitrogen not only serves for inducing tetragonality in α′-Fe8Nx but is also essential for achieving a high degree of perpendicular magneto-crystalline anisotropy, K. Our results demonstrate that the orbital magnetic moments of the iron atoms above and below N in the direction of magnetization are much more susceptible to the applied magnetic field than their in-plane counterparts, leading to a giant value of K as compared to a hypothetical distorted material without N.

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confidence: 79%

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confidence: 99%

Engineering perpendicular magnetic anisotropy in Fe via interstitial nitrogenation: N choose K

et al. 2016

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“…Let us compare Fe 16 bct-Fe, where even for c/a = 1.1 (the c/a ratio for Fe 16 N 2 ) MAE is still rather tiny. 40 In Fig. 7 the calculated MAE in Fe 16 N 2 is shown as a function of c/a.…”

Section: Magnetic Anisotropymentioning

confidence: 99%

Effects of alloying and strain on the magnetic properties of Fe16N2

Belashchenko

Schilfgaarde

et al. 2013

Phys. Rev. B

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The electronic structure and magnetic properties of pure and doped Fe 16 N 2 systems have been studied in the local-density (LDA) and quasiparticle self-consistent GW approximations. The GW magnetic moment of pure Fe 16 N 2 is somewhat larger compared to LDA but not anomalously large. The effects of doping on magnetic moment and exchange coupling were analyzed using the coherent potential approximation. Our lowest estimate of the Curie temperature in pure Fe 16 N 2 is significantly higher than the measured value, which we mainly attribute to the quality of available samples and the interpretation of experimental results. We found that different Fe sites contribute very differently to the magnetocrystalline anisotropy energy (MAE), which offers a way to increase the MAE by small site-specific doping of Co or Ti for Fe. The MAE also increases under tetragonal strain.

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“…This MAE, which is larger by 3 orders of magnitude than for bcc Fe, occurs theoretically for a composition of about Fe 0:4 Co 0:6 and c=a 1:20-1:25. Also, the predicted easy axis of magnetization for the tetragonal alloy is along the c axis, which facilitates the usage in perpendicular magnetic recording applications.The mechanism responsible for this giant MAE has been identified by an analysis of the electronic states at the ÿ point at the center of the Brillouin zone, which govern the MAE of tetragonal Fe [4,6]. When the cubic symmetry is broken through tetragonal distortion, electronic states that are degenerate in the cubic state will split and cross other states when the c=a ratio is around 1.2.…”

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“…When the cubic symmetry is broken through tetragonal distortion, electronic states that are degenerate in the cubic state will split and cross other states when the c=a ratio is around 1.2. From a second order perturbation treatment of the MAE it follows that a strongly enhanced K u can be expected if the alloy concentration is chosen such that the Fermi energy is at the band crossing [4,6]. …”

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Perpendicular Magnetocrystalline Anisotropy in Tetragonally Distorted Fe-Co Alloys

et al. 2006

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We report on the experimental realization of tetragonal Fe-Co alloys as a constituent of Fe 0:36 Co 0:64 =Pt superlattices with huge perpendicular magnetocrystalline anisotropy energy, reaching 210 eV=atom, and a saturation magnetization of 2:5 B =atom at 40 K, in qualitative agreement with theoretical predictions. At room temperature the corresponding values 150 eV=atom and 2:2 B =atom are achieved. This suggests that Fe-Co alloys with carefully chosen combinations of composition and distortion are good candidates for high-density perpendicular storage materials. DOI: 10.1103/PhysRevLett.96.037205 PACS numbers: 75.30.Gw, 75.50.Bb, 75.50.Ss The enormous increase in the recording density of hard disk drives, by more than 6 orders of magnitude during the past 50 years, has mainly been achieved by simply scaling the dimensions of the bits recorded in the storage layer [1]. However, this traditional scaling is limited by the onset of superparamagnetism. This occurs when the grain volume V in the recording medium is reduced so that the ratio of the magnetic energy per grain to the thermal energy, K u V=k B T, becomes sufficiently small to cause the recorded data to be erased by thermal fluctuations in an intolerably short time [1,2]. K u is the uniaxial magnetocrystalline anisotropy energy (MAE), i.e., the energy required for rotating the magnetization direction from an easy axis to the hard axis. Thus, high-K u materials [3] are needed to further increase the recording density. The maximum practical MAE, however, is limited by the required write field H w K u =M s , which has to be delivered by the writing head. Thus, a large value of M s , the saturation magnetization of the recording medium, will be beneficial both through decreasing H w as well as by increasing the field available in the readback process. Hence, large values of K u and M s are indispensable properties of future high-density magnetic recording materials.Recently, based on first-principles calculations, tetragonal Fe-Co alloys were proposed as promising materials that combine the desired large values of K u and M s [4]. The advantages of the suggested alloys, as compared to other materials considered for magnetic storage [3], are their about 50% larger saturation magnetization, the huge perpendicular MAE, and the possibility to tailor the MAE by changing the alloy concentration. In addition, Fe-Co alloys do not require as high deposition temperatures as, e.g., chemically ordered L1 0 FePt [5], which has received considerable attention recently. From the calculations it was found that, for certain values of the ratio c=a, between the lengths of the body-centered tetragonal (bct) crystal's c and a axes, and for specific alloy concentrations, very high values of K u 800 eV=atom can be expected. This MAE, which is larger by 3 orders of magnitude than for bcc Fe, occurs theoretically for a composition of about Fe 0:4 Co 0:6 and c=a 1:20-1:25. Also, the predicted easy axis of magnetization for the tetragonal alloy is along the c axis, which facilitat...

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Erratum: Calculation of uniaxial magnetic anisotropy energy of tetragonal and trigonal Fe, Co, and Ni [Phys. Rev. B69, 104426 (2004)]

Abstract: The matrix describing a trigonal distortion [Eq.(2)] is erroneous. It should read:where d is chosen to conserve the unit-cell volume. The calculations, however, were done with the correct matrix, so this change has no effect on the results or conclusions.

Cited by 24 publications

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Engineering perpendicular magnetic anisotropy in Fe via interstitial nitrogenation: N choose K

Engineering perpendicular magnetic anisotropy in Fe via interstitial nitrogenation: N choose K

Effects of alloying and strain on the magnetic properties of Fe16N2

Perpendicular Magnetocrystalline Anisotropy in Tetragonally Distorted Fe-Co Alloys

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