Magnetic reversal in three-dimensional exchange-spring permanent magnets

Shield, Jeffrey E.; Zhou, Jian; Aich, Shampa; Ravindran, V.; Skomski, Ralph; Sellmyer, David J.

doi:10.1063/1.2163837

Cited by 17 publications

(15 citation statements)

References 22 publications

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“…One such active field of research is the exchange spring magnet [3][4][5][6][7] , where high saturation magnetization of the soft and the high magnetic anisotropy of the hard magnetic phases are exchange coupled in the nanometric scale. Both the experimental studies and the Micromagnetic calculations [8][9][10][11] reveal that significant improvements in terms of magnetic energy product (BH) max can be achieved using the exchange spring magnet.…”

Section: Introductionmentioning

confidence: 99%

Investigation on non-exchange spring behaviour and exchange spring behaviour: A first order reversal curve analysis

Roy¹,

Sreenivasulu²,

Kumar³

2013

Applied Physics Letters

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The magnetization behaviour of the soft Cobalt Ferrite-hard Strontium Ferrite nanocomposite is tuned from the non exchange spring nature to the exchange spring nature, by controlling the particle size of the soft Cobalt Ferrite in the Cobalt Ferrite: Strontium Ferrite (1:8) nanocomposite. The relative strength of the interaction governing the magnetization process in the nanocomposites is investigated using Henkel plot and First Order Reversal Curve (FORC) method. The FORC method has been utilized to understand the magnetization reversal behaviour as well as the extent of the irreversible magnetization present in both the nanocomposites having smaller and larger particle size of the Cobalt Ferrite. The magnetization process is primarily controlled by the domain wall movement in the nanocomposites. Using the FORC distribution in the (H a , H b ) co-ordinate, the onset of the nucleation field, invasion of the domain wall from the soft to the hard phase, domain wall annihilation and the presence of the reversible magnetization with the applied reversal field for both the nanocomposites has been investigated. It has been found that for the composite having lower particle size of the soft phase shows a single switching behaviour corresponding to the coherent reversal of the both soft and hard phases. However, the composite having higher Cobalt Ferrite particle size shows two peak behaviour in the FORC distribution resembling individual switching of the soft and hard phases. The FORC distribution in (H u , H c ) co-ordinate and the Henkel measurement confirms the dominant exchange interaction in the nanocomposites exhibiting exchange spring behaviour where as the occurrence of both the dipolar and exchange interaction is substantiated for the non exchange coupled nanocomposite. The asymmetric nature of the FORC distribution at H c = 0 Oe for both the nanocomposites validates the intercoupled nature of the reversible and irreversible magnetizations in both the nanocomposites. It is also concluded that the contribution of the reversible magnetization is more in the nanocomposite having lower particle size of the Cobalt Ferrite compared to the nanocomposite having higher particle size of the Cobalt Ferrite.

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Section: Introductionmentioning

confidence: 99%

Investigation on non-exchange spring behaviour and exchange spring behaviour: A first order reversal curve analysis

Roy¹,

Sreenivasulu²,

Kumar³

2013

Applied Physics Letters

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“…NdFeB rare earth permanent magnets have been widely used in many industrial fields, such as aeronautics, astronautics, automotive, appliance, computers, and communications, thanks to their excellent magnetic property [1][2][3]. Sintered NdFeB permanent magnets are brittle and with poor mechanical properties.…”

Section: Introductionmentioning

confidence: 99%

Influences of Laser Spot Welding on Magnetic Property of a Sintered NdFeB Magnet

Chang

et al. 2016

Metals

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Laser welding has been considered as a promising method to join sintered NdFeB permanent magnets thanks to its high precision and productivity. However, the influences of laser welding on the magnetic property of NdFeB are still not clear. In the present paper, the effects of laser power on the remanence (Br) were experimentally investigated in laser spot welding of a NdFeB magnet (N48H). Results show that the Br decreased with the increase of laser power. For the same welding parameters, the Br of magnets, that were magnetized before welding, were much lower than that of magnets that were magnetized after welding. The decrease in Br of magnets after laser welding resulted from the changes in microstructures and, in turn, the deterioration of magnetic properties in the nugget and the heat affected zone (HAZ) in a laser weld. It is recommended that the dimensions of nuggets and HAZ in laser welds of a NdFeB permanent magnet should be as small as possible, and the magnets should be welded before being magnetized in order to achieve a better magnetic performance in practical engineering applications.

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“…1,2 Since then EB has been observed in a vast variety of systems including AF/FM and FM/ferrimagnetic thin-film heterostructures, AF/FM core shell nanoparticles, FM precipitates in AF and spin glass matrices, and spin valves; but details of its origin still remains elusive to date. [3][4][5][6][7] Similar to exchange-spring magnets, [8][9][10][11] AF coupled bilayers of soft and hard FM films show exchange-induced coupling phenomena analogous to conventional EB heterolayers. 4,[12][13][14] The FM hard layer ͑HL͒ pins the magnetically soft layer ͑SL͒ and shifts its hysteresis loops along the magnetic-field axis.…”

Section: Introductionmentioning

confidence: 99%

Temperature dependence of the training effect in exchange coupled ferromagnetic bilayers

et al. 2008

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The temperature dependence of the training effect is studied in an exchange coupled thin-film bilayer composed of a hard ferromagnetic pinning ͑CoPtCrB͒ layer in proximity of a soft ferromagnetic pinned ͑CoCr͒ layer. Interlayer exchange shifts the hysteresis loops of the soft layer along the magnetic-field axis. This shift is quantified by the bias field in far reaching analogy to the exchange bias field of conventional antiferromagnetic/ferromagnetic heterostructures. A ferromagnetic domain state induced in the hard layer experiences aging very similar to the training behavior of the antiferromagnetic domain state in conventional exchange bias systems. Training originates from changes in the spin structure of the pinning layer with consecutive magnetization reversals of the pinned layer. Here we perform a detailed investigation of the temperature dependence of the bias field and its training effect. Consecutively cycled hysteresis loops of the soft layer are measured at various temperatures. We also derive a theoretical description of the temperature dependence of the training effect which is in agreement with the experimental data.

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Magnetic reversal in three-dimensional exchange-spring permanent magnets

Cited by 17 publications

References 22 publications

Investigation on non-exchange spring behaviour and exchange spring behaviour: A first order reversal curve analysis

Investigation on non-exchange spring behaviour and exchange spring behaviour: A first order reversal curve analysis

Influences of Laser Spot Welding on Magnetic Property of a Sintered NdFeB Magnet

Temperature dependence of the training effect in exchange coupled ferromagnetic bilayers

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