The magnetocrystalline anisotropy of cobalt

Paige, D.M.; Szpunar, Barbara; Tanner, B. K.

doi:10.1016/0304-8853(84)90248-8

Cited by 102 publications

(34 citation statements)

References 26 publications

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“…2͑e͒ and 2͑f͔͒ suggest a slight tendency for an easy axis of magnetization parallel to the wires. Because the crystalline anisotropy of hcp Co decreases at higher temperature 19 the saturation fields parallel to the wires decrease at higher temperatures.…”

Section: Resultsmentioning

confidence: 99%

Structure and magnetization of arrays of electrodeposited Co wires in anodic alumina

Strijkers

Dalderop

Broeksteeg

et al. 1999

Journal of Applied Physics

165

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We have produced arrays of Co nanowires in anodic porous alumina filters by means of electrodeposition. The structure and magnetization behavior of the wires was investigated with nuclear magnetic resonance ͑NMR͒ and magnetization measurements. NMR shows that the wires consist of a mixture of fcc and hcp texture with the ͑0001͒ texture of the hcp fraction oriented preferentially perpendicular to the wires. The magnetization direction is determined by a competition of demagnetizing fields and dipole-dipole fields and can be tuned parallel or perpendicular to the wires by changing the length of the wires.

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Section: Resultsmentioning

confidence: 99%

Structure and magnetization of arrays of electrodeposited Co wires in anodic alumina

Strijkers

Dalderop

Broeksteeg

et al. 1999

Journal of Applied Physics

165

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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. The MAE depends on subtle differences in the electronic structure under rotations of the external magnetic field.…”

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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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“…According to the recent study of magnetocrystalline anisotropy constants in hcp'Co made by Paige et al [4], the value determined by using the least mean square routine has been confirmed. This method has extensively applied in the case of unsaturated torque curves in NdzFe14B intermetallic compound [5,6] of which the magnetocrystalline anisotropy constants are one order of magnitude larger than in hcp Co. To check the applicability of the new method, measurements and analysis have been made for hcp Co in a very low magnetic field range.…”

Section: Introductionmentioning

confidence: 80%

“…4 and 1.7 T. The d i f f e r e n c e b e t w e e n t h e l o w f i e l d and t h e h i g h f i e l d v a l u e s i s w i t h i n 0.5%, which i s u n e x p e c t e d l y s m a l l , w h i l e t h e s l o p e o f t h e l i n e a r p a r t above 0.3 T can be detected.…”

Section: Analysis Of Torque Curvesmentioning

confidence: 99%

Torque curve measurements in HCP Co in very low fields

Ono

1987

IEEE Trans. Magn.

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Magnetic torque measurements have been made for a single crystal of Co of hcp structure in a very low field region where the torque intensity was not saturated. I n this region it had been considered to be impossible to determine the magnetocrystalline anisotropy constants from observed torque curves. Recently, a new method of analyzing the torque curves was proposed by the present author with the help of a least mean square routine instead of the usual Fourier analysis. By using this method the first magnetocrystalline anisotropy constant Kul was, for the first time, determined at 77 K. It was found that the Kul determined in the low field range between 0.3 and 0.5 T coincides with the value determined at a high field region where the torque curve was saturated enough. Below 0.2 T the value of Kul decreased with decreasing the field. This region was found to correspond to the domain wall formation.

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The magnetocrystalline anisotropy of cobalt

Cited by 102 publications

References 26 publications

Structure and magnetization of arrays of electrodeposited Co wires in anodic alumina

Structure and magnetization of arrays of electrodeposited Co wires in anodic alumina

Calculation of magnetic anisotropy energy inSmCo5

Torque curve measurements in HCP Co in very low fields

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