Magnetic Anisotropy of Some Nickel Zinc Ferrite Crystals

Groenou, A. Broese van; Schulkes, J.A.; Annis, D. A.

doi:10.1063/1.1709512

Cited by 45 publications

(10 citation statements)

References 8 publications

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“…11a, show a well defined, relatively narrow, maximum for the M ZFC curve at T B = 12 K and an irreversibility temperature above room temperature. This difference in the values of T B and T irr is consistent with a very broad particle size distribution, as already observed by TEM, and indicates that a non negligible fraction of nanoparticles is still blocked at 300 K. Fitting the blocking temperature distribution to a log-normal one and considering an average value of about (3.0 ± 0.9) kJ/m 3 [49][50][51][52] for the bulk NiZn ferrite magnetic anisotropy constant, the mean particle size results in (14 ± 4) nm, which corresponds to the large-particle size-tail of the P l distribution. At temperatures below the maximum, the ZFC curve exhibits a rapid increase and above the maximum at T B , a monotonic decrease following a Curie-Weiss-like law, as expected for a superparamagnetic behavior.…”

Section: 4supporting

confidence: 82%

Ni0.5Zn0.5Fe2O4 nanoparticles dispersed in a SiO2 matrix synthesized by sol–gel processing

López¹,

Condó²,

Urreta³

et al. 2012

Materials Characterization

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Section: 4supporting

confidence: 82%

Ni0.5Zn0.5Fe2O4 nanoparticles dispersed in a SiO2 matrix synthesized by sol–gel processing

López¹,

Condó²,

Urreta³

et al. 2012

Materials Characterization

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“…For example [84], in the case of nanoparticles of Ni-Zn ferrite with a diameter of 10 nm, considering the value of the constant K s which is of the order of 10 À5 Jm À2 [85], the value obtained for K' s is 6 Â 10 3 Jm À3 . This value is five times higher than the magnetocrystalline anisotropy constant (1,5 Â 10 3 Jm À3 [86]) of Ni-Zn ferrite. In conclusion, in the case of small nanoparticles, the contribution of the spins at the surface layer of nanoparticles to the magnetic anisotropy becomes important, sometimes even dominant.…”

Section: Magnetic Anisotropy Of Nanoparticlesmentioning

confidence: 80%

Nanoparticle Size Effect on Some Magnetic Properties

Caizer

2015

Handbook of Nanoparticles

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Nanoparticles exhibit, from a magnetic point of view, various anomalies and specific magnetic properties, different from those of the bulk with the same chemical composition. Knowing the new magnetic properties is very important, both from theoretical point of view and their numerous practical applications in nanotechnology (nanotechnics and, recently, in nanomedicine), which should be considered. In this chapter we shall present an overview on the following topics: saturation magnetization, magnetic anisotropy, and magnetic behavior of magnetic nanoparticles, in relation with their size and magnetic structure, single-or multi-domains. The magnetic properties of the nanoparticles are compared and discussed in relation to those of the corresponding bulk. The surface effects, in the case of surfacted nanoparticles and those embedded in different matrices, on magnetic properties are presented and discussed in the core-shell model (core of the nanoparticle, where the magnetic moments are aligned under the exchange interaction, and the shell, where the magnetic moments are in a disordered structure).In the case of small (nm to tens of nm), single-domain nanoparticles (without a structure of magnetic domains), their volume is generally smaller than a magnetic domain (Weiss domain), domain in which the magnetic moments from the crystalline network are aligned (ordered) spontaneously at saturation.:This result (Eq. 79) shows that the critical field (coercive field in this case) decreases as the magnetic diameter of the nanoparticles decreases, and becomes zero at the threshold diameter (D m = D mt ). Experimental results broadly confirm the law of variation (Eq. 79) in the range D m =D mt ¼ 1 À 5 ð Þ. Kneller and Luborsky [132] found a good concordance between the calculated and experimental values Handbook of Nanoparticles

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“…4(a) shows the hysteresis loops of sample A at 5 and 300 K. At 5 K, a ferrimagnetic loop is observed, with a saturation magnetization (M s ) of 93 emu/g and a coercive field (H c ) of 62 Oe (inset at left). M s is slightly lower than the magnetization of the bulk ($ 113 emu/g [4]), while H c (more clearly observed in the left upper inset) is about half the anisotropy field (H K $ 125 Oe [4,5]), which can be expected for nanoparticles in the single domain range. At room temperature, the magnetization as a function of applied field exhibits a superparamagnetic shape with no coercive field (right lower inset in Fig.…”

Section: Resultsmentioning

confidence: 96%