Crystal-field anisotropy of Sm3+ in SmCo5

Buschow, K.H.J.; Diepen, A. M. van; Wijn, H. W. de

doi:10.1016/0038-1098(74)90690-5

Cited by 119 publications

(27 citation statements)

References 5 publications

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“…All higher-order crystal field parameters were taken equal to zero here. Further calculations [6] have shown that their effects are relatively small. It is finally noted, that the effect of J-mixing is to increase the anisotropy by about one third.…”

Section: (29)mentioning

confidence: 96%

Samarium in Crystal Fields, a Case of Strong J‐Mixing

Wijn¹,

Diepen

Buschow

1976

Physica Status Solidi (b)

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Section: (29)mentioning

confidence: 96%

Samarium in Crystal Fields, a Case of Strong J‐Mixing

Wijn¹,

Diepen

Buschow

1976

Physica Status Solidi (b)

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“…Experimental information is readily available for large band-gap rare-earth insulators, where the CFP can be extracted from measurements of dipole-forbidden optical transitions between f -states. 15 In the case of rareearth intermetallics, where the f − f transitions are hidden by the optical response of conduction electrons, inelastic neutron spectroscopy can be used to determine CFP, [16][17][18][19][20] but its results are more ambiguous as one needs to sort out the contributions of phonons and the effect of inter-site exchange interactions.…”

Section: -6mentioning

confidence: 99%

“…We validate it by applying it to the well-known hard magnet SmCo 5 , for which the crystal-field splitting has been measured in multiple experiments. [16][17][18][19][20] We then apply our method to much less investigated new hard magnets of the RFe 12 X family, computing their CFP for different rare-earth elements (Sm or Nd) and considering N and Li interstitials. Our calculations predict the hypothetical SmFe 12 Li compound to possess a strong axial anisotropy and, possibly, interesting hard-magnetic properties.…”

mentioning

confidence: 99%

Crystal-field splittings in rare-earth-based hard magnets: Anab initioapproach

Delange

Biermann

Miyake³

et al. 2017

Phys. Rev. B

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We apply the first-principles density functional theory + dynamical mean field theory framework to evaluate the crystal-field splitting on rare-earth sites in hard magnetic intermetallics. An atomic (Hubbard-I) approximation is employed for local correlations on the rare-earth 4f shell and selfconsistency in the charge density is implemented. We reduce the density functional theory selfinteraction contribution to the crystal-field splitting by properly averaging the 4f charge density before recalculating the one-electron Kohn-Sham potential. Our approach is shown to reproduce the experimental crystal-field splitting in the prototypical rare-earth hard magnet SmCo5. Applying it to RFe12 and RFe12X hard magnets (R =Nd, Sm and X =N, Li), we obtain in particular a large positive value of the crystal-field parameter A 0 2 r 2 in NdFe12N resulting in a strong out-of-plane anisotropy observed experimentally. The sign of A 0 2 r 2 is predicted to be reversed by substituting N with Li, leading to a strong out-of-plane anisotropy in SmFe12Li. We discuss the origin of this strong impact of N and Li interstitials on the crystal-field splitting on rare-earth sites.

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“…24 . What is important for our discussion is that both experimental and calculated numbers are substantially larger than the MAE of the hcp Co (0.065 meV/Co) 25 We can actually pinpoint the microscopic origin of this large MAE.…”

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confidence: 99%

Calculation of magnetic anisotropy energy inSmCo5

2003

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SmCo5 is an important hard magnetic material, due to its large magnetic anisotropy energy (MAE). We have studied the magnetic properties of SmCo5 using density functional theory (DFT) calculations where the Sm f -bands, which are difficult to include in DFT calculations, have been treated within the LDA+U formalism. The large MAE comes mostly from the Sm f -shell anisotropy, stemming from an interplay between the crystal field and the spin-orbit coupling. We found that both are of similar strengths, unlike some other Sm compounds, leading to a partial quenching of the orbital moment (f -states cannot be described as either pure lattice harmonics or pure complex harmonics), an optimal situation for enhanced MAE. A smaller portion of the MAE can be associated with the Co-d band anisotropy, related to the peak in the density of states at the Fermi energy. Our result for the MAE of SmCo5, 21.6 meV/f.u., agrees reasonably with the experimental value of 13-16 meV/f.u., and the calculated magnetic moment (including the orbital component) of 9.4µB agrees with the experimental value of 8.9µB .The permanent magnet intermetallic compound SmCo 5 has been studied extensively experimentally 1,2 and theoretically [3][4][5][6][7][8][9][10][11] . The interest in these materials is fueled by their large magnetic anisotropy energy (MAE), which is defined as the difference between the groundstate energies due to rotation of the magnetic field (magnetization direction). It is generally understood that the main source of the large MAE in SmCo 5 and other SmCo magnets is large magnetic single-site anisotropy of the Sm f -shell 9,12-14 . In simple terms, this means the strong spin-orbit coupling tries to align the Sm f -shell with the magnetic field, causing the f -shell to rotate with the field. Sm atoms in a lattice interact with the crystal field, and the energy of this interaction depends on the orientation of the Sm f -shell in the lattice. This is the leading contribution to the MAE. Note that if the crystal field is too small, the f -shell rotates freely with the magnetic field, producing no MAE, while if the spin-orbit is too small, the orbital moment is quenched and again no MAE appears. We will see below that in SmCo 5 both interactions are comparable, producing a large MAE.This basic understanding has existed for long time, and has been the basis of several model calculations, where atomic calculations for Sm have been combined with the crystal field parameters derived from first principles calculations 15 . However, first principles calculations which could provide a quantitative analysis of different components of MAE in SmCo 5 are still missing, to the best of our knowledge. In this paper we report such calculations, using an all-electron, full-potential, relativistic linearized augmented plane wave (FLAPW) method with an LDA+U extension to account for Coulomb correlations in the f -shell.Our analysis is organized as follows: We start by looking at the "Co part" of the MAE, the part not related to the Sm single-site aniso...

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Crystal-field anisotropy of Sm3+ in SmCo5

Cited by 119 publications

References 5 publications

Samarium in Crystal Fields, a Case of Strong J‐Mixing

Samarium in Crystal Fields, a Case of Strong J‐Mixing

Crystal-field splittings in rare-earth-based hard magnets: Anab initioapproach

Calculation of magnetic anisotropy energy inSmCo5

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