Estimation of the Co nanoparticles size by magnetic measurements in Co/SiO2 discontinuous multilayers

Micha, Jean‐Sébastien; Diény, B.; Regnard, J. R.; Jacquot, Jean-François; Sort, Jordi

doi:10.1016/j.jmmm.2003.12.268

Cited by 60 publications

(48 citation statements)

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“…Figure 4 shows the temperature dependence of the ZFC and FC magnetizations in the range of 5 to 300 K for both samples. Following the ZFC and FC curves, one can determine the mean blocking temperature (defined as the d(FC -ZFC)/dT maximum value) (Micha et al 2004) at about 107 and 110 K for the FT and GA samples, respectively. These values are close to those obtained from the measurement of the coercive field temperature dependence.…”

Section: Resultsmentioning

confidence: 99%

Magnetic properties study of iron-oxide nanoparticles/PVA ferrogels with potential biomedical applications

et al. 2013

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A study of the magnetic behavior of maghemite nanoparticles (NPs) in polyvinyl alcohol (PVA) polymer matrices prepared by physical crosslinking is reported. The magnetic nanocomposites (ferrogels) were obtained by the in situ co-precipitation of iron salts in the presence of PVA polymer, and subsequently subjected to freezing-thawing cycles. The magnetic behavior of these ferrogels was compared with that of similar systems synthesized using the glutaraldehyde. This type of chemical crosslinking agents presents several disadvantages due to the presence of residual toxic molecules in the gel, which are undesirable for biological applications. Characteristic particle size determined by several techniques are in the range 7.9-9.3 nm. The iron oxidation state in the NPs was studied by X-ray absorption spectroscopy. Mössbauer measurements showed that the NP magnetic moments present collective magnetic excitations and superparamagnetic relaxations. The blocking and irreversibility temperatures of the NPs in the ferrogels, and the magnetic anisotropy constant, were obtained from magnetic measurements. An empirical model including two magnetic contributions (large NPs slightly departed from thermodynamic equilibrium below 200 K, and small NPs at thermodynamic equilibrium) was used to fit the experimental magnetization curves. A deviation from the superparamagnetic regime was observed. This deviation was explained on the basis of an interacting superparamagnetic model. From this model, relevant magnetic and structural properties were obtained, such as the magnitude order of the dipolar interaction energy, the NPs magnetic moment, and the number of NPs per ferrogel mass unit. This study contributes to the understanding of the basic physics of a new class of materials that could emerge from the PVA-based magnetic ferrogels.

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Section: Resultsmentioning

confidence: 99%

Magnetic properties study of iron-oxide nanoparticles/PVA ferrogels with potential biomedical applications

et al. 2013

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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

216

122

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“…Therefore, a pronounced peak in the ZFC curve is the onset of blocking from superparamagnetism, whereas ZFC and FC curves coincide at high temperature and split at a temperature where relaxation time becomes comparable to measurement time. An alternative approach proposed by Micha et al to estimate superparamagnetic blocking temperature ( T B SP ) is to calculate the maximum of temperature derivative of ZFC/FC difference [−d( M FC − M ZFC )/d T ], where there has been a finite probability for moments to become unblocked and unblocked moments begin to contribute more to magnetization than the blocked ones. Remarkably, T B SP < T irr and they are both lower than ZFC peak temperature.…”

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confidence: 99%

Spin‐Glass Irreversibility Temperature and Magnetic Stabilization in Ferromagnet/Spin‐Glass Bilayers

2019

Physica Rapid Research Ltrs

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The authors numerically studied the irreversibility temperature (Tirr) of a spin glass (SG) and how to use a SG to stabilize a ferromagnet. The rate of Tirr/SG‐anisotropic‐field increment can reach ≈121 K T−1. In ferromagnet/SG bilayers, exchange bias (EB) may be enhanced fivefold at 10 K with increasing interfacial coupling (JIF), whereas the EB blocking temperature (TBEB) does not change. However, decreases in SG exchange coupling (JSG) can twofold enhance TBEB with maintaining a table‐like EB. On the contrary, small JIF and large JSG are both destructive to coercivity. Nevertheless, EB field and coercivity are switchable, opening an opportunity to design temperature‐controlled write‐to‐read switches.

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Estimation of the Co nanoparticles size by magnetic measurements in Co/SiO2 discontinuous multilayers

Cited by 60 publications

References 1 publication

Magnetic properties study of iron-oxide nanoparticles/PVA ferrogels with potential biomedical applications

Magnetic properties study of iron-oxide nanoparticles/PVA ferrogels with potential biomedical applications

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

Spin‐Glass Irreversibility Temperature and Magnetic Stabilization in Ferromagnet/Spin‐Glass Bilayers

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