High energy products in rapidly annealed nanoscale Fe/Pt multilayers

Liu, J. P.; Luo, Chuanfu; Liu, Y.; Sellmyer, David J.

doi:10.1063/1.120793

Cited by 316 publications

(174 citation statements)

References 10 publications

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“…They are potential high-density recording media [1][2][3] and high-energy permanent magnets 4 because of their exceptional magnetic properties. The essential feature is that they can undergo a phase transition from the disordered face-centered cubic ͑fcc͒ structure to the ordered facecentered tetragonal ͑fct͒ structure (L1 0 phase͒ after postdeposition annealing, 1 or when deposited at an elevated substrate temperature.…”

mentioning

confidence: 99%

Nanostructured FePt:B2O3 thin films with perpendicular magnetic anisotropy

Luo

Liou

Gao

et al. 2000

Applied Physics Letters

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215

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FePt/B 2 O 3 multilayers were deposited by magnetron sputtering onto 7059 glass substrates. By annealing the as-deposited films at 550 °C, nanostructured FePt:B2O3 films consisting of FePt grains with L10 structure, embedded in a glassy B2O3 matrix, were obtained. The c axes of the FePt grains can be made to align with the film normal direction, which results in a perpendicular anisotropy constant of 3.5×107 erg/cc. The films remain layered structures after annealing when the B2O3 layer thickness exceeds 16 Å. The nanostructure of the films was investigated by transmission electron microscopy. The coercivities and the average grain sizes of the films are dependent on the B2O3 concentrations, with coercivities varying from 4 to 12 kOe, while average grain sizes vary from 4 to 17 nm. Strong perpendicular anisotropy, adjustable coercivity, and fine grain size suggest this nanocomposite system might have significant potential as recording media at extremely high areal density.

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mentioning

confidence: 99%

Nanostructured FePt:B2O3 thin films with perpendicular magnetic anisotropy

Luo

Liou

Gao

et al. 2000

Applied Physics Letters

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215

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“…1 On this basis, room-temperature energy products as high as about 400 kJ/m 3 ͑50 MGOe͒ have recently been obtained in iron-rich two-phase Pt-Fe thin films. 2 This energy product is close to energy products of the present record-holder Nd 2 Fe 14 B and clearly exceeds energy products achieved in single-phase PtFe materials.…”

mentioning

confidence: 63%

“…To obtain a reasonable (BH) max value, Liu et al 2 used an approximate skewing procedure based on the assumption of an infinite slope dM /dHϭϱ at HϭH c , 10 and obtained (BH) max ϭ52.8 MGOe for Dϭ0.48. The approximate character of this method is evident from a simple counter-example: an ensemble of independent particles having a very broad distribution of coercivities exhibits dM /dHϾ0 at HϭH c , independently of the strength of the demagnetizing field.…”

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confidence: 99%

Hysteresis-loop overskewing in the light of a novel nucleation mode

Skomski

Liu

Sellmyer

2000

Journal of Applied Physics

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It is demonstrated that the magnetostatic demagnetizing factor is not the only sample-shape dependent contribution to the hysteresis loop. There are also exchange contributions, which lead to interesting effects, particularly in nanostructures. An example is the recently discovered bulging mode in two-phase nanomagnets. The bulging mode exhibits the angular symmetry of the coherent mode, but it is incoherent due to its radial variation and gives rise to negative demagnetizing factors.

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“…14 A potentially very useful semihard material is Co 3 Pt with experimental anisotropies of the order of 2 MJ/ m 3 ͑20 ergs/ cm 3 ͒. The orthorhombic Pmm2 phase of Co 3 Pt has an anisotropy of about 2.8 MJ/ m 3 ͑28 ergs/ cm 3 ͒, but its equilibrium formation requires a strain of more than 1%. 15 A system with very high interface anisotropies is Fe/W͑110͒.…”

Section: Semihard Phasesmentioning

confidence: 99%

“…The energy product of aligned two-phase magnets [1][2][3] exhibits a practical limitation due to the dependence of the coercivity on the local anisotropy K 1 ͑r͒, so that theoretical energy products are difficult to achieve. In two-phase permanent magnets, which are usually composed of hard and soft phases, the main role of the soft phase is to enhance the magnetization.…”

Section: Introductionmentioning

confidence: 99%

Graded permanent magnets

Skomski

Hadjipanayis

Sellmyer

2009

Journal of Applied Physics

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The effect of semihard magnetic phases and interfaces on the performance of nanostructured two-phase permanent magnets is investigated by model calculations. In addition to the trivial coercivity increase due to the replacement of soft regions by semihard regions, there is a coercivity enhancement even if the volume-averaged anisotropy is kept constant during the introduction of the semihard phase. A variational approach is used to derive analytical results for representative anisotropy profiles. The improvement is operative on length scales slightly larger than that of the soft phase in hard-soft composites, but the main challenge is to find semihard light or heavy transition metal phases with a high magnetization. There are several Fe-and Co-based phases, but most are thin-film systems and difficult to use in bulk magnets. Very hard nanostructured magnets may also be created from soft phases with negative but large anisotropy constants ͑hard-magnetic soft-soft magnets͒.

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High energy products in rapidly annealed nanoscale Fe/Pt multilayers

Cited by 316 publications

References 10 publications

Nanostructured FePt:B2O3 thin films with perpendicular magnetic anisotropy

Nanostructured FePt:B2O3 thin films with perpendicular magnetic anisotropy

Hysteresis-loop overskewing in the light of a novel nucleation mode

Graded permanent magnets

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