Magnetic susceptibility curves of a nanoparticle assembly II. Simulation and analysis of ZFC/FC curves in the case of a magnetic anisotropy energy distribution

Tournus, Florent; Tamion, Alexandre

doi:10.1016/j.jmmm.2010.11.057

Cited by 65 publications

(31 citation statements)

References 26 publications

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“…Some authors maintain the IP criterion, 10 while others report the maximum ZFC magnetization temperature (MAX); 11,12 both criteria are still under discussion. [13][14][15] In an alternative approach, Micha et al 16 propose a method in which the T B distribution is obtained from the T derivative of the difference between ZFC and FC curves. An approximated theoretical justification for this method was presented by Mamiya et al 17 In this work, a SW model with thermal agitation is applied to obtain the temporal dependence of the magnetization M(t) of an ordered system of identical MNPs in a similar way to the previous works of Lu, 18 Usov,19 and Carrey.…”

Section: Introductionmentioning

confidence: 99%

Determination of the blocking temperature of magnetic nanoparticles: The good, the bad, and the ugly

Bruvera

Zélis

Calatayud

et al. 2015

Journal of Applied Physics

220

122

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Section: Introductionmentioning

confidence: 99%

Determination of the blocking temperature of magnetic nanoparticles: The good, the bad, and the ugly

Bruvera

Zélis

Calatayud

et al. 2015

Journal of Applied Physics

220

122

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“…We used the semianalytical model presented in Ref. [38] and the magnetic moments of Tables I and II as input. For both phases, the mean magnetic diameter coincides within the error with the geometric one; see Table III.…”

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confidence: 99%

Low Temperature Ferromagnetism in Chemically Ordered FeRh Nanocrystals

et al. 2013

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In sharp contrast to previous studies on FeRh bulk, thin films, and nanoparticles, we report the persistence of ferromagnetic order down to 3 K for size-selected 3.3 nm diameter nanocrystals embedded into an amorphous carbon matrix. The annealed nanoparticles have a B2 structure with alternating atomic Fe and Rh layers. X-ray magnetic dichroism and superconducting quantum interference device measurements demonstrate ferromagnetic alignment of the Fe and Rh magnetic moments of 3 and 1 B , respectively. The ferromagnetic order is ascribed to the finite-size induced structural relaxation observed in extended x-ray absorption spectroscopy. DOI: 10.1103/PhysRevLett.110.087207 PACS numbers: 75.30.Kz, 75.75.Cd, 81.07.Bc Iron-rhodium alloys exhibit competing ferromagnetic (FM) and antiferromagnetic (AFM) phases with transition temperatures close to ambient for nearly equiatomic composition and body-centered-cubic (bcc) CsCl-like B2 structure. The competition between the two magnetic orders of FeRh holds great potential in spintronics and heat assisted magnetic recording [1,2]. Moreover, the peculiar bulk FeRh magnetic phase diagram enables its use as active material in heat pumps and refrigerators [3][4][5].At ambient conditions, bulk B2 FeRh is a G-type AFM with a total magnetic moment on the iron atoms of 3:3 B and no appreciable moment on the rhodium atoms [6][7][8]. Above the transition temperature of 370 K, the atomic moments of Fe and Rh are ferromagnetically aligned and take on total values of 3.2 and 0:9 B , respectively [6][7][8]. While it has long been known that the bcc unit cell volume expands by % 1% upon transforming to FM order [9], recent experiments suggest that distortions of the bcc structure may occur [10]. Given the itinerant character of the 3d electrons, the coupling between crystallographic and magnetic order in this system is both rich and very delicate as demonstrated by the theoretical challenge to model the system [11], as well as by recent pump-probe experiments focusing on ultrafast magnetization control [12].Finite-size systems of this alloy have received particular attention by their potential to stabilize the FM phase at room temperature and below. Strained thin films [13,14] showed traces of a FM phase down to 300 K, while ab initio calculations predicted FM down to 0 K for a Rh-terminated 9 ML FeRh(001) film [15] and for 8-atom FeRh clusters [16]. Indeed, since nanosized crystals may present significantly different interatomic distances and unit cell distortions with respect to bulk [17,18], a fundamentally modified magnetic phase diagram can be expected for FeRh nanocrystals. However, the first experiments on chemically synthesized FeRh nanoparticles (NPs) failed to evidence low temperature stability of the FM phase. Most notably, they raised important questions, such as partial B2 ordering, elemental segregation, and coalescence upon annealing [19][20][21].In this Letter, we demonstrate the persistence of FM order down to below 3 K in size-selected FeRh nanocrystals with a mean d...

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“…The consequence is an erroneous interpretation of experimental data, and this was what we wanted to point out in our article. 3 To make it short, it was not the formula which was erroneous, but its (frequent) usage. Therefore, pointing towards a "frequent error met in the literature" was not a misconception.…”

Section: Particle Size Distribution and Probability Density Functmentioning

confidence: 99%

“…1 "Another confusing result in Ref. 12 is the effect of f 0 on the vðTÞ variation, which was considered not to be an important issue," whereas the influence of f 0 had been examined in our articles 2,3 (the f 0 dependence is explicitly given in the expression of T B and T X for instance) and we had written "many couples of f 0 and FIG. 1.…”

Section: "Blocking" Temperature Distributionmentioning

confidence: 99%

“…It is explained that the "volume and number weighted distribution are equally valid for the representation of distribution functions in nanoparticle magnetic systems" and the usual modelling approach (abrupt transition from a blocked to a superparamagnetic regime, at a given temperature) is compared to the more elaborate one (the "progressive crossover model (PCM)") introduced in our previous articles. [2][3][4] The importance of the f 0 value is also stressed. In this article, several statements are made in opposition to some of our previously published results.…”

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confidence: 99%

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Comment on “Nano-particle magnetism with a dispersion of particle sizes” [J. Appl. Phys. 112, 103915 (2012)]

Tournus¹,

Tamion²

2013

Journal of Applied Physics

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A recent paper1 examines zero field-cooled/field-cooled (ZFC/FC) susceptibility curves for nanoparticle assemblies with a size distribution. It is explained that the “volume and number weighted distribution are equally valid for the representation of distribution functions in nanoparticle magnetic systems” and the usual modelling approach (abrupt transition from a blocked to a superparamagnetic regime, at a given temperature) is compared to the more elaborate one (the “progressive crossover model (PCM)”) introduced in our previous articles.2–4 The importance of the f0 value is also stressed. In this article, several statements are made in opposition to some of our previously published results. Because we like to believe that these words were driven by a simple “misunderstanding” of our models and analysis, we would like to clarify some points in the present comment.

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Magnetic susceptibility curves of a nanoparticle assembly II. Simulation and analysis of ZFC/FC curves in the case of a magnetic anisotropy energy distribution

Cited by 65 publications

References 26 publications

Determination of the blocking temperature of magnetic nanoparticles: The good, the bad, and the ugly

Determination of the blocking temperature of magnetic nanoparticles: The good, the bad, and the ugly

Low Temperature Ferromagnetism in Chemically Ordered FeRh Nanocrystals

Comment on “Nano-particle magnetism with a dispersion of particle sizes” [J. Appl. Phys. 112, 103915 (2012)]

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