Random magnetocrystalline anisotropy in two-phase nanocrystalline systems

Suzuki, Kiyonori; Cadogan, J. M.

doi:10.1103/physrevb.58.2730

Cited by 259 publications

(141 citation statements)

References 24 publications

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“…Under the assumption that a polycrystalline nanoparticle of a small diameter, D < D c , has strictly uniform magnetization, it is possible to determine 27,28 the direction of the effective easy anisotropy axis of the particle and to calculate the value of the corresponding effective anisotropy constant. In agreement with the random anisotropy model, [29][30][31][32] the latter turns out to be much smaller than the original value of uniaxial anisotropy constant of single-crystal hcp cobalt. This is due to averaging of the anisotropic interactions in a polycrystalline nanoparticle.…”

Section: Resultssupporting

confidence: 57%

“…For such polycrystalline nanoparticles an approximate estimate of the effective magnetic anisotropy constant was made 27,28 based on the random anisotropy model. [29][30][31][32] Unfortunately, to date the statistics of the single-crystal granules in polycrystalline nanoparticles is still poorly investigated experimentally. In this paper, to investigate the magnetic properties of polycrystalline nanoparticles we adopt a simple model where the particle volume is randomly decomposed into N g = 4 -16 crystallites of various sizes.…”

Section: Introductionmentioning

confidence: 99%

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Magnetic properties of polycrystalline cobalt nanoparticles

et al. 2017

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The energy diagram of stationary magnetization states existing in polycrystalline cobalt nanoparticles in the range of diameters 20 ≤ D ≤ 60 nm has been calculated by means of numerical simulation. It is shown that in polycrystalline cobalt nanoparticles in the range of diameters D ≥ 32 nm only vortex states with low average magnetization are present, whereas mostly quasi-uniform states are realized in nanoparticles with diameter D ≤ 24 nm. Thus, the effective single-domain diameter of polycrystalline cobalt nanoparticles is estimated to be Dc = 24 nm. It is approximately two times smaller than the actual single-domain diameter of monocrystalline cobalt nanoparticle, Dc0 = 45 nm. The hysteresis loops of a dilute assembly of polycrystalline cobalt nanoparticles in the range of diameters D ≤ Dc are characterized by a coercive force that is approximately 2.5 times less compared with that of the randomly oriented assembly of monocrystalline cobalt nanoparticles.

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Section: Resultssupporting

confidence: 57%

Section: Introductionmentioning

confidence: 99%

Magnetic properties of polycrystalline cobalt nanoparticles

et al. 2017

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“…13,14 In this context, the magnetocrystalline anisotropy averages out due to the small size of the crystallites (smaller than the exchange length) and it can be written as a function of the magnetocrystalline anisotropy, K 1 , the exchange stiffness, A, and the microstructural parameters D and X C 13 hKi ¼ 3 4…”

mentioning

confidence: 99%

Influence of microstructure on the enhancement of soft magnetic character and the induced anisotropy of field annealed HITPERM-type alloys

Blázquez

Marcin

Varga

et al. 2015

Journal of Applied Physics

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“…An increase of the both remanence and coercive field, has been previously reported in nanocrystalline Fe 91 Zr 7 B 2 , 15 with crystalline fraction around 50%. Nonetheless our samples are amorphous within the accuracy provided by x-ray and neutron ͑see below͒ diffraction as well as Möss-bauer spectroscopy.…”

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confidence: 90%

Thermoremanence anomaly in Fe-Zr(B,Cu) Invar metallic glasses: Volume expansion induced ferromagnetism

et al. 2000

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We report the existence of a thermally induced sharp increase of thermoremanence around the Curie temperature of Invar-like Fe-Zr͑B,Cu͒ soft magnetic glasses. Neutron-diffraction measurements indicate that a true enhancement of the average local magnetic moment, rather than only a change in the domain structure, occurs. Such enhancement has been tentatively attributed to the increasing volume expansion that takes place beyond the Curie temperature and reinforces ferromagnetism in some low-density clusters.The origin of the complex magnetic properties of ironrich metallic glasses containing low concentrations of early transition metals ͑Zr,Sc,Hf,Y͒ have attracted considerable interest during more than two decades, giving rise to several controversial microscopic interpretations. [1][2][3][4] In particular Fe x Zr 100Ϫx amorphous alloys with x above 80 at.% rank among the most extensively studied spin system, 5-10 exhibiting weak itinerant ferromagnetism, low-temperature spinglass-like behavior and Invar character.Nowadays it is clear that Invar-like iron-rich Fe x Zr 100Ϫx , as well as Fe-Zr͑B,Cu͒, 12 soft magnetic glasses exhibit: ͑i͒ a sharp increase of the thermal expansion above the Curie temperature, T C , 2,3 ͑ii͒ a large high-field susceptibility, 5 ͑iii͒ a decrease in both the magnetic moment and T C with increasing x, 9 ͑iv͒ a large positive spontaneous volume magnetostriction, 11 ͑v͒ a positive shift in T C with the tensile stress, 12 and a large but negative shift with pressure. 2,3 Moreover, it is well established that, as a consequence of competitive positive and negative interactions, the spontaneous magnetization is low and the effect of the field is to induce local magnetic moment, as pointed out by the high volume magnetostriction at low fields. 11 In addition, due to the sensitivity of the local magnetic moment to the interatomic distances, the spontaneous magnetization is expected to fluctuate with density fluctuations which are always present in amorphous structures. The sign of the magnetic interactions depends on the interatomic distances giving rise to the coexistence of complex magnetic phases and in this way both cluster 13 and frustration 8 microscopic models have been proposed to account for the overall behavior. According to the positive volume magnetostriction experimentally observed, 11 it is accepted that those regions or clusters with lower local density should exhibit the higher local magnetic moment and thus stronger ferromagnetic character. On the other hand, spinglass-like regions with higher density will surround these ferromagnetic clusters so decreasing the average local magnetic moment.In this work we present the highlights of a detailed experimental study regarding the thermoremanence behavior in amorphous Fe-Zr͑B,Cu͒ which confirms the appearance of a reversible magnetic transition that occurs around their Curie points. 10 were produced in the form of ribbons, with approximate thicknesses of 20 m, using the melt spinning technique. The amorphous structure of all the samp...

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Random magnetocrystalline anisotropy in two-phase nanocrystalline systems

Cited by 259 publications

References 24 publications

Magnetic properties of polycrystalline cobalt nanoparticles

Magnetic properties of polycrystalline cobalt nanoparticles

Influence of microstructure on the enhancement of soft magnetic character and the induced anisotropy of field annealed HITPERM-type alloys

Thermoremanence anomaly in Fe-Zr(B,Cu) Invar metallic glasses: Volume expansion induced ferromagnetism

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