Slow relaxation in ferromagnetic nanoparticles: Indication of spin-glass behavior

Ulrich, Markus; Garcı́a-Otero, J.; Rivas, José; Bunde, Armin

doi:10.1103/physrevb.67.024416

Cited by 179 publications

(169 citation statements)

References 19 publications

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“…These features can be successfully modeled in the framework of the motion of a pinned DW in a random FM exhibiting relaxation, creep, slide and switching [11,27,28,30]. (2) Another strong indication of SFM behavior can be found from analyzing relaxation curves of the thermoremanent magnetic moment, m vs. t. Ulrich et al [31] introduce a universal relaxation behavior for any nanoparticle system according to a decay law of the form…”

Section: Superferromagnetic (Sfm) Orderingmentioning

confidence: 99%

Collective states of interacting ferromagnetic nanoparticles

Petracic

Chen

Bedanta

et al. 2006

Journal of Magnetism and Magnetic Materials

164

129

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Discontinuous magnetic multilayers [CoFe/Al 2 O 3 ] are studied by use of magnetometry, susceptometry and numeric simulations. Soft ferromagnetic Co 80 Fe 20 nanoparticles are embedded in a diamagnetic insulating a-Al 2 O 3 matrix and can be considered as homogeneously magnetized superspins exhibiting randomness of size (viz. moment), position and anisotropy. Lacking intra-particle core-surface ordering, generic freezing processes into collective states rather than individual particle blocking are encountered. With increasing particle density one observes first superspin glass and then superferromagnetic domain state behavior. The phase diagram resembles that of a dilute disordered ferromagnet. Criteria for the identification of the individual phases are given.

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Section: Superferromagnetic (Sfm) Orderingmentioning

confidence: 99%

Collective states of interacting ferromagnetic nanoparticles

Petracic

Chen

Bedanta

et al. 2006

Journal of Magnetism and Magnetic Materials

164

129

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“…In this context, the magnetic properties of assemblies of magnetic interacting particles have been studied by Monte Carlo simulations, 8 and recently Ulrich et al 9 have found that the relaxation rate of the thermoremanent magnetic moment of such assemblies follows an universal power-law. Depending on the value of the exponent, it is found stretched exponential decay for diluted magnetic particles and algebraic decay for concentred ones.…”

Section: Introductionmentioning

confidence: 99%

Power-law decay in first-order relaxation processes

2005

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Starting from a simple definition of stationary regime in first-order relaxation processes, we obtain that experimental results are to be fitted to a power-law when approaching the stationary limit. On the basis of this result we propose a graphical representation that allows the discrimination between power-law and stretched exponential time decays. Examples of fittings of magnetic, dielectric and simulated relaxation data support the results. 76.20.+q, 76.90.+d, 75.40.Mg

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“…Simulations of the zero-field cooling (ZFC) and field-cooling susceptibility showed no indication of a spinglass phase [6,7]. In contrast, simulations on aging [8] (on a simplified system, where the dipolar interaction was only considered up to a cut-off radius) and magnetic relaxation [9,10] favorize the spin-glass hypothesis, but the structure of the frozen history-dependent states as well as the actual mechanism leading to them has not yet been clarified.…”

Section: Introductionmentioning

confidence: 99%

Ising-like dynamics and frozen states in systems of ultrafine magnetic particles

Russ

Bunde

2007

Phys. Rev. B

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We use Monte-Carlo simulations to study aging phenomena and the occurence of spinglass phases in systems of single-domain ferromagnetic nanoparticles under the combined influence of dipolar interaction and anisotropy energy, for different combinations of positional and orientational disorder. We find that the magnetic moments oriente themselves preferably parallel to their anisotropy axes and changes of the total magnetization are solely achieved by 180 degree flips of the magnetic moments, as in Ising systems. Since the dipolar interaction favorizes the formation of antiparallel chain-like structures, antiparallel chain-like patterns are frozen in at low temperatures, leading to aging phenomena characteristic for spin-glasses. Contrary to the intuition, these aging effects are more pronounced in ordered than in disordered structures.

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Slow relaxation in ferromagnetic nanoparticles: Indication of spin-glass behavior

Cited by 179 publications

References 19 publications

Collective states of interacting ferromagnetic nanoparticles

Collective states of interacting ferromagnetic nanoparticles

Power-law decay in first-order relaxation processes

Ising-like dynamics and frozen states in systems of ultrafine magnetic particles

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