A nanoparticle replica of the spin-glass state

Toro, J. A. De; Lee, Su Seong; Salazar, Daniel; Cheong, Jian Liang; Normile, P. S.; Muniz, Pablo Rodrigues; Riveiro, José Manuel Suárez; Hillenkamp, Matthias; Tournus, Florent; Tamion, Alexandre; Nordblad, Per

doi:10.1063/1.4804187

Cited by 72 publications

(77 citation statements)

References 31 publications

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“…The calculated values p ¼ 0.022 and p ¼ 0.046 for the low temperature maxima in both samples Co/Au1, Co/Au2, respectively, were from the interval 0.005e0.05. Various superspin glass systems with p parameter from this interval were reported [12], thus the observed properties can be regarded as collective freezing of superspins. On the other hand, the value calculated for the second maximum in Co/ Au2 p ¼ 0.092 approximated the interval typical of pure superspin blocking process 0.1e0.13 [29].…”

Section: Ac Magnetic Susceptibilitymentioning

confidence: 97%

“…Several theoretical and empirical models for ac susceptibility data evaluation were introduced and their results provide the information on character of magnetic relaxation as well as on the strength of inter-particle interactions [5,6,12,13,22]. The assembly of magnetic nanoparticles can exhibit different behavior depending on the strength of possible interactions between particles.…”

Section: Ac Magnetic Susceptibilitymentioning

confidence: 99%

“…With increasing interaction strength the relaxation time does not follow the Ne el-Arrhenius law, Eq. (1) and some authors [12,13,24] employ the Vogel-Fulcher law for data evaluation. According to this model the relaxation time is determined by the equation [22].…”

Section: Ac Magnetic Susceptibilitymentioning

confidence: 99%

“…However, the origin of the interactions controlling the magnetic ordering is completely different in both cases. De Toro et al [11,12] observed the ideal superspin glass behavior in the ensemble of uniform 8 nm maghemite nanoparticles after they had been pressed into the disc. On the other hand, Tadic et al [13] presented non-compressed maghemite nanoparticles (4 nm) which exhibited superparamagnetic properties.…”

Section: Introductionmentioning

confidence: 99%

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The study of magnetic properties and relaxation processes in Co/Au bimetallic nanoparticles

Hrubovčák

Zeleňáková

Zeleňák

et al. 2015

Journal of Alloys and Compounds

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Section: Ac Magnetic Susceptibilitymentioning

confidence: 97%

Section: Ac Magnetic Susceptibilitymentioning

confidence: 99%

Section: Ac Magnetic Susceptibilitymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

The study of magnetic properties and relaxation processes in Co/Au bimetallic nanoparticles

Hrubovčák

Zeleňáková

Zeleňák

et al. 2015

Journal of Alloys and Compounds

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“…Nevertheless most of them have been worked out in superferromagnetic/super spin glass state 9,10,65,66 . The latter scenario is very close to the one in milled alloys of GdAl 2 18 and TbAl 2 20,22 for which the ferromagnetic transition was disappearing at the expense of a growing SG state.…”

mentioning

confidence: 99%

Magnetic phase diagram of superantiferromagnetic TbCu₂nanoparticles

Echevarria-Bonet

Rojas

Espeso

et al. 2015

J. Phys.: Condens. Matter

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The structural state and static and dynamic magnetic properties of TbCu2 nanoparticles are reported. The nanoparticles were produced by mechanical milling under inert atmosphere with low milling times ≤ 15 hours. The randomly dispersed nanoparticles as detected by TEM retain the bulk symmetry with an orthorhombic Imma lattice and Tb and Cu in 4c positions. Rietveld refinements confirm that the milling produces a controlled reduction of particle sizes reaching down to ≃ 6 nm and an increase of the microstrain ≃ 0.6 %. The DC-susceptibility shows a reduction of the Néel transition (from 49 K to 43 K) and a progressive increase of the spin glass peak (from 9 to 15 K) in the zero field cooled magnetization with size reduction. The exchange anisotropy is very weak (bias field of ≃ 30 Oe) and is due to the presence of a disordered (thin) shell coupled to the antiferromagnetic core. The dynamic susceptibility evidences a critical slowing down in the spin disordered state with a tendency to increase of zv and β exponents when the size becomes smaller (zv ≃ 6.6 and β ≃ 0.85). A Rietveld analysis of neutron diffraction patterns 1.8 ≤ T ≤ 60 K including the magnetic structure determination reveals that there is a reduction of the expected moment (≃ 80 %) which must be connected to the presence of the disordered particle shell. The core magnetic structure retains the bulk antiferromagnetic arrangement. The overall interpretation is based on a superantiferromagnetic behavior which at low temperatures coexists with a canting of surface moments. We propose a novel magnetic phase diagram as a function of the particle size.

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Detailed magnetic monitoring of the enhanced magnetism of ferrihydrite along its progressive transformation into hematite

et al. 2016

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Under certain aging conditions, ferrihydrite evolves into hematite through intermediate products of enhanced magnetism. Although the magnetic properties of the end product, hematite, are to date satisfactorily known, those of ferrihydrite (and especially the products of its progressive aging) are not sufficiently explored. To this end, magnetic experiments, conducted mostly by using alternating magnetic fields, have been performed. The results reveal that two‐line ferrihydrite exhibits conspicuous low‐temperature spin glass behavior, a new finding that, on the other hand, could be expected given the previous microstructural observations that described this mineral as a very disordered gel. Upon aging, a progressive increase of the effective magnetic moment per iron ion is detected, in agreement with previous observations that ascribed ferrimagnetic character to an intermediate crystalline phase (sometime called ferriferrihydrite) that disappears just before the full transformation into hematite. Transmission electron microscopy observations suggest that this intermediate crystalline phase nucleates at the expense of the primordial gel, remaining physically attached to it until complete transformation into hematite. This microstructural picture appears well supported as, upon aging, the glassy magnetic dynamics found in ferrihydrite persists for the aged products even when dispersed in a nonmagnetic matrix, very likely because part of the so grown ferrimagnetic nanoparticles form aggregates within remains of the nontransformed gel. We propose a coherent model of ferrihydrite aging, based on integrated microstructural and magnetic observations, which is useful for the identification of aging products in geological and biological environments.

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A nanoparticle replica of the spin-glass state

Cited by 72 publications

References 31 publications

The study of magnetic properties and relaxation processes in Co/Au bimetallic nanoparticles

The study of magnetic properties and relaxation processes in Co/Au bimetallic nanoparticles

Magnetic phase diagram of superantiferromagnetic TbCu₂nanoparticles

Detailed magnetic monitoring of the enhanced magnetism of ferrihydrite along its progressive transformation into hematite

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A nanoparticle replica of the spin-glass state

Cited by 72 publications

References 31 publications

The study of magnetic properties and relaxation processes in Co/Au bimetallic nanoparticles

The study of magnetic properties and relaxation processes in Co/Au bimetallic nanoparticles

Magnetic phase diagram of superantiferromagnetic TbCu2nanoparticles

Detailed magnetic monitoring of the enhanced magnetism of ferrihydrite along its progressive transformation into hematite

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Magnetic phase diagram of superantiferromagnetic TbCu₂nanoparticles