Magnetic Properties and Crystal Structures of FePt Nanoparticle Media

Kodama, Hiroyoshi; Momose, Satoru; Uzumaki, Takuya; Tanaka, Atsushi

doi:10.3379/jmsjmag.28.372

Cited by 72 publications

(94 citation statements)

References 14 publications

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“…However, in case of nanoparticles, it is reported that the temperature dependence of the magnetization follows a T 2 law rather than the usual Bloch's T 3/2 law [36]. The deviation from the T 3/2 dependence observed in the magnetic nanoparticles is due to the finite-size effects and, in particular, the energy gap in the density of states and lack of magnetic coordination at the surface of the nanoparticles [37,38]. However, it is found that M(T) data for the present as-prepared NiFe 2 O 4 nanoparticles could not be fitted using the modified Bloch's T 2 law.…”

Section: Magnetic Studiesmentioning

confidence: 95%

Cation distribution and enhanced surface effects on the temperature-dependent magnetization of as-prepared NiFe2O4 nanoparticles

Nadeem

Siddique

2015

Appl. Phys. A

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Nickel ferrite, i.e., NiFe 2 O 4 , nanoparticles are synthesized by sol-gel method using urea as a neutralizing agent. The formation of spinel phase and crystal structure of the as-prepared sample is analyzed by X-ray diffraction and transmission electron microscope. In order to confirm phase formation and cation arrangement, room temperature 57 Fe Mössbauer spectroscopy is employed. The degree of inversion (i) estimated from the relative peak area is found to be 0.6, which confirms a mixed spinel structure of the asprepared sample. Zero-field-cooled/field-cooled measurements showed evidence of superparamagnetic behavior associated with the nanosized particles. Hysteresis loop measurements revealed temperature-dependent magnetic properties: The coercive field (H C ) decreases with increasing temperature and deviates from the Kneller's law for ferromagnetic nanostructures; and the saturation magnetization (M s ) follows modified Bloch's law in the temperature range between 25 and 400 K. However, below 25 K, an abrupt increase in magnetization of nanoparticles is observed. In order to understand this behavior, an additional contribution has to be added to the core magnetization to properly fit the data. Hence, a surface correction term to the Bloch's law is found to describe the temperature dependence of magnetization in the core-shell NiFe 2 O 4 nanoparticles.

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Section: Magnetic Studiesmentioning

confidence: 95%

Cation distribution and enhanced surface effects on the temperature-dependent magnetization of as-prepared NiFe2O4 nanoparticles

Nadeem

Siddique

2015

Appl. Phys. A

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“…The atoms on the surface have truncated bonds and less coordination neighbors, thus their mutual exchange interaction is reduced [25]. Kodama et al [26,27] have proposed a model of non-coherent magnetization within these particles consisting of a ferrimagnetically aligned core and a disordered surface spin layer. A much lower saturation magnetization for the coated nanoparticles may be due to a stronger disorder of surface spins and the presence of SiO 2 (forming a diamagnetic matrix which "dilutes" the magnetization of the otherwise compacted ferrite particles).…”

Section: Silica Coated Nanoparticles Synthesized Using Sol-gel Methodsmentioning

confidence: 99%

Comparison of surface effects in SiO2 coated and uncoated nickel ferrite nanoparticles

Nadeem

Krenn

Sarwar

et al. 2014

Applied Surface Science

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“…This comparison is only indicative and should be cautiously criticized in the case of complex microstructures. It is known that the saturation magnetization is highly dependent on magnetic particle interactions with the matrix in the case of composite materials and on magnetic particle concentrations within the matrix, concentrations which govern the interactions and coupling between particles [45,46]. In our case, the iron oxide concentration is relatively low and thus is not problematic.…”

Section: Magnetic Properties By Squidmentioning

confidence: 78%

Magnetic and in vitro heating properties of implants formed in situ from injectable formulations and containing superparamagnetic iron oxide nanoparticles (SPIONs) embedded in silica microparticles for magnetically induced local hyperthermia

Renard

Lortz

Senatore

et al. 2011

Journal of Magnetism and Magnetic Materials

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a b s t r a c tThe biological and therapeutic responses to hyperthermia, when it is envisaged as an anti-tumor treatment modality, are complex and variable. Heat delivery plays a critical role and is counteracted by more or less efficient body cooling, which is largely mediated by blood flow. In the case of magnetically mediated modality, the delivery of the magnetic particles, most often superparamagnetic iron oxide nanoparticles (SPIONs), is also critically involved. We focus here on the magnetic characterization of two injectable formulations able to gel in situ and entrap silica microparticles embedding SPIONs. These formulations have previously shown suitable syringeability and intratumoral distribution in vivo. The first formulation is based on alginate, and the second on a poly(ethylene-co-vinyl alcohol) (EVAL). Here we investigated the magnetic properties and heating capacities in an alternating magnetic field (141 kHz, 12 mT) for implants with increasing concentrations of magnetic microparticles. We found that the magnetic properties of the magnetic microparticles were preserved using the formulation and in the wet implant at 37 1C, as in vivo. Using two orthogonal methods, a common SLP (20 W g À 1 ) was found after weighting by magnetic microparticle fraction, suggesting that both formulations are able to properly carry the magnetic microparticles in situ while preserving their magnetic properties and heating capacities.

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Magnetic Properties and Crystal Structures of FePt Nanoparticle Media

Cited by 72 publications

References 14 publications

Cation distribution and enhanced surface effects on the temperature-dependent magnetization of as-prepared NiFe2O4 nanoparticles

Cation distribution and enhanced surface effects on the temperature-dependent magnetization of as-prepared NiFe2O4 nanoparticles

Comparison of surface effects in SiO2 coated and uncoated nickel ferrite nanoparticles

Magnetic and in vitro heating properties of implants formed in situ from injectable formulations and containing superparamagnetic iron oxide nanoparticles (SPIONs) embedded in silica microparticles for magnetically induced local hyperthermia

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