Iron nanowires embedded in mesoporous silica: Polarized neutron scattering study

Grigorieva, N.A.; Grigoriev, S. V.; Okorokov, A. I.; Eckerlebe, H.; Eliseev, A. A.; Lukashin, A. V.; Napolskii, K. S.

doi:10.1016/j.physe.2005.03.003

Cited by 9 publications

(4 citation statements)

References 12 publications

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“…To reduce the unwanted crystallite coarsening and particles aggregation, attempts have been made to synthesize nanocomposites by embedding ferrite nanoparticles in a suitable matrix [23]. Different matrixes such as resins [24], polymer films [25] and silica glasses [26,27] have been studied. Studies on magnetic nanocomposites of ferrite nanoparticles dispersed in the silica matrix [28,29] have revealed a behavior different from that of bulk systems.…”

Section: Introductionmentioning

confidence: 99%

Influence of calcination temperature on structural and magnetic properties of nanocomposites formed by Co-ferrite dispersed in sol-gel silica matrix using tetrakis(2-hydroxyethyl) orthosilicate as precursor

Gharagozlou

2011

Chemistry Central Journal

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Effects of calcination temperatures varying from 400 to 1000°C on structural and magnetic properties of nanocomposites formed by Co-ferrite dispersed in the sol-gel silica matrix using tetrakis(2-hydroxyethyl) orthosilicate (THEOS) as water-soluble silica precursor have been investigated. Studies carried out using XRD, FT-IR, TEM, STA (TG-DTG-DTA) and VSM techniques. Results indicated that magnetic properties of samples such as superparamagnetism and ferromagnetism showed great dependence on the variation of the crystallinity and particle size caused by the calcination temperature. The crystallization, saturation magnetization Ms and remenant magnetization Mr increased as the calcination temperature increased. But the variation of coercivity Hc was not in accordance with that of Ms and Mr, indicating that Hc is not determined only by the crystallinity and size of CoFe2O4 nanoparticles. TEM images showed spherical nanoparticles dispersed in the silica network with sizes of 10-30 nm. Results showed that the well-established silica network provided nucleation locations for CoFe2O4 nanoparticles to confinement the coarsening and aggregation of nanoparticles. THEOS as silica matrix network provides an ideal nucleation environment to disperse CoFe2O4 nanoparticles and thus to confine them to aggregate and coarsen. By using THEOS as water-soluble silica precursor over the currently used TEOS and TMOS, the organic solvents are not needed owing to the complete solubility of THEOS in water. Synthesized nanocomposites with adjustable particle sizes and controllable magnetic properties make the applicability of Co-ferrite even more versatile.

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Section: Introductionmentioning

confidence: 99%

Influence of calcination temperature on structural and magnetic properties of nanocomposites formed by Co-ferrite dispersed in sol-gel silica matrix using tetrakis(2-hydroxyethyl) orthosilicate as precursor

Gharagozlou

2011

Chemistry Central Journal

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“…Since SANS is utilized in diverse fields of science such as biology, chemistry, physics or materials science, there exists an enormous body of research literature and, therefore, any realistic attempt to provide an encyclopedic listing is beyond the scope of this work. Magnetic SANS has been used to study a wide range of materials, including ferrofluids [20][21][22][23][24][25][26][27][28][29], nanoparticles and precipitates [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49], nanowires [50,51], magnetic recording media [52][53][54][55], collossal magnetoresistance materials [56][57][58], spin glasses and amorphous metals [59][60][61][62][63][64][65][66]…”

Section: Introductionmentioning

confidence: 99%

Magnetic-field-dependent small-angle neutron scattering on random anisotropy ferromagnets

Michels

Weißmüller

2008

Rep. Prog. Phys.

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We report on the recently developed technique of magnetic-field-dependent small-angle neutron scattering (SANS), with attention to bulk ferromagnets exhibiting random magnetic anisotropy. In these materials, the various magnetic anisotropy fields (magnetocrystalline, magnetoelastic, and/or magnetostatic in origin) perturb the perfectly parallel spin alignment of the idealized ferromagnetic state. By varying the applied magnetic field, one can control one of the ordering terms which competes with the above-mentioned perturbing fields. Experiments which explore the ensuing reaction of the magnetization will therefore provide information not only on the field-dependent spin structure but, importantly, on the underlying magnetic interaction terms. This strategy, which underlies conventional studies of hysteresis loops in magnetometry, is here combined with magnetic SANS. While magnetometry generally records only a single scalar quantity, the integral magnetization, SANS provides access to a vastly richer data set, the Fourier spectrum of the response of the spin system as a function of the magnitude and orientation of the wave vector. The required data-analysis procedures have recently been established, and experiments on a number of magnetic materials, mostly nanocrystalline or nanocomposite metals, have been reported. Here, we summarize the theory of magnetic-field-dependent SANS along with the underlying description of random anisotropy magnets by micromagnetic theory. We review experiments which have explored the magnetic interaction parameters, the value of the exchange-stiffness constant as well as the Fourier components of the magnetic anisotropy field and of the magnetostatic stray field. A model-independent approach, based on the experimental autocorrelation function of the spin misalignment, provides access to the characteristic length of the spin misalignment. The field dependence of this quantity is in quantitative agreement with the predictions of micromagnetic theory. Experiments on nanocomposite ferromagnets reveal that the jump of the magnetization at internal phase boundaries leads to a significant magnetostatic perturbing field, with an unusual 'clover-leaf' SANS pattern as the experimental signature. Furthermore, SANS experiments have been used to monitor the orientation of magnetic domains as well as the length scale of intradomain spin misalignment.

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“…The measurements reveal a large hysteresis in the field dependent part of the cross section I H (q). This type of behaviour under a magnetic field applied perpendicularly to nanowires is quite typical and was observed in samples with Fe embedded in silicon oxide (Grigorieva et al, 2005). This complex behaviour is caused by interplay of the Zeeman energy (interaction between the magnetic moment and the field) and the large structural anisotropy.…”

Section: Resultsmentioning

confidence: 53%

“…The small-angle scattering (q < 0.04 nm À1 ) increases significantly in samples with Ni. In our opinion, this scattering is caused by the imperfectness of the Ni nanowires inhomogeneously grown within pores (Grigorieva et al, 2005).…”

Section: Resultsmentioning

confidence: 89%

Polarized small-angle neutron scattering study of two-dimensional spatially ordered systems of nickel nanowires

et al. 2007

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The magnetic and structural properties of two-dimensional spatially ordered systems of ferromagnetic nickel nanowires embedded into an Al 2 O 3 matrix have been studied using polarized small-angle neutron scattering (polarized SANS). We measured the total (nuclear and magnetic) scattering I(q) as a polarizationindependent scattering, the field-dependent scattering as I H (q) = I(q, H) À I(q, 0), where H is the magnetic field, and the nuclear-magnetic interference as a polarization-dependent (P) scattering ÁI(q, P). A typical scattering pattern is composed of the diffuse small-angle scattering and the Bragg peak. It is shown that the introduction of Ni into the matrix does not change the position of the Bragg peak but results in an increase of the scattering intensity both in the smallangle region and at the Bragg positions. An external magnetic field was applied perpendicular or parallel to the long dimension of the nanowires in order to reveal the anisotropic properties of the magnetic system. It is shown that, firstly, the magnetic-field-dependent scattering I H (q) provides new and principally different information as compared with the interference term ÁI(q). Secondly, two contributions to the interference term ÁI(q) (ascribed to the diffuse scattering and to the diffraction peaks) have different signs indicating different origins of the scattering objects. Thirdly, polarized SANS gives a detailed picture of the magnetization process, which could not be obtained by methods of standard magnetometry.

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Iron nanowires embedded in mesoporous silica: Polarized neutron scattering study

Cited by 9 publications

References 12 publications

Influence of calcination temperature on structural and magnetic properties of nanocomposites formed by Co-ferrite dispersed in sol-gel silica matrix using tetrakis(2-hydroxyethyl) orthosilicate as precursor

Influence of calcination temperature on structural and magnetic properties of nanocomposites formed by Co-ferrite dispersed in sol-gel silica matrix using tetrakis(2-hydroxyethyl) orthosilicate as precursor

Magnetic-field-dependent small-angle neutron scattering on random anisotropy ferromagnets

Polarized small-angle neutron scattering study of two-dimensional spatially ordered systems of nickel nanowires

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