Superferromagnetism in chain-like Fe@SiO2 nanoparticle ensembles

Zeleňáková, A.; Zeleňák, Vladimı́r; Maťko, I.; Strečková, M.; Hrubovčák, Pavol; Kováč, J.

doi:10.1063/1.4890354

Cited by 30 publications

(25 citation statements)

References 41 publications

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“…1D assemblies of magnetic nanoparticles can be prepared by soft templating based on organic molecules or bacteria or by hard templating based on mesoporous silica . Chain of nanoparticles induced by a magnetic field can also be retained by silica coating or attractive interactions due to polymer coating . Besides these approaches, 1D structures have been mostly prepared via magnetic‐field‐induced assembly which is usually combined with the drop casting of a nanoparticle suspension.…”

Section: Introductionmentioning

confidence: 99%

Enhanced Collective Magnetic Properties Induced by the Controlled Assembly of Iron Oxide Nanoparticles in Chains

Toulemon

Rastei

Schmool

et al. 2016

Adv Funct Materials

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1D assemblies of magnetic nanoparticles are of great potential for designing novel nanostructured materials with enhanced collective magnetic properties. In that challenging context, a new assembly strategy is presented to prepare chains of magnetic nanoparticles that are well‐defined in structure and in spatial arrangement. The 1D assembly of iron oxide nanoparticles onto a substrate is controlled using “click” chemistry under an external magnetic field. Co‐aligned single nanoparticle chains separated by regular distances can be obtained by this strategy. The intrinsic high uniaxial anisotropy results in a strong enhancement of magnetic collective properties in comparison to 2D monolayers or isolated nanoparticles. In contrast to the intensively studied bundle chains of nanoparticles, the finely tuned chain structure reported here allows evidencing a first order intrachain dipolar interaction and a second order interchain magnetic coupling. This study offers new insights into the collective magnetic properties of highly anisotropic particulate assemblies which have been investigated by combining superconducting quantum interference device magnetometry, magnetic force microscopy, and ferromagnetic resonance.

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Section: Introductionmentioning

confidence: 99%

Enhanced Collective Magnetic Properties Induced by the Controlled Assembly of Iron Oxide Nanoparticles in Chains

Toulemon

Rastei

Schmool

et al. 2016

Adv Funct Materials

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“…The magnetic properties of long chain FeCo NP assemblies were similar to Fe@SiO 2 chain-like nanocompostie and their ferromagnetic performance (shown in figure 4) was also due to SFM effect between superspins' exchange interaction. The FeCo NPs with anisotropic long chain structure in this work had higher remanence ratio (∼0.53) than that of the isotropic one (∼0.28), 17 indicating the orientation and strong exchange coupling between NPs in anisotropic long chains. In figure 1, well crystallized FeCo alloy NPs show cubic shape which can have more contact area with other NPs compared to the spherical ones.…”

Section: Methodsmentioning

confidence: 84%

“…Other researchers also reported long chain NP assemblies with ferromagnetic properties even though the chains were isotropic instead of anisotropic as we reported in this work. Zeleňáková et al 17 reported that the 4 nm Fe NP chain-like structure with SiO 2 shell showing hysteresis at room temperature though 4 nm Fe NP itself was superparamagnetic. The long chain Fe@SiO 2 sample had coercivity of 200 Oe at 300 K and the remanence ratio M r /M s was around 0.28, indicating that even the superparamagnetic Fe NPs could show ferromagnetic behavior due to strong exchange interactions between NPs in the long chain structure.…”

Section: Methodsmentioning

confidence: 99%

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Magnetic properties of cubic FeCo nanoparticles with anisotropic long chain structure

Liu

Wang

2016

AIP Advances

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Cubic FeCo alloy nanoparticles (NPs) with body-centered cubic (bcc) phase were prepared using sputter based gas-condensation method. When the NPs formed long chain assemblies, the magnetic properties were quite different from that of well-dispersed NPs. Most of the well-dispersed NPs were superparamagnetic at room temperature while the long chain NP assemblies were ferromagnetic with coercivities around 765 Oe, which displayed quite different magnetic properties. The ferromagnetism of long chain NPs was from the exchange coupling between NPs, which eventually led to the transition from superparamagnetism (SPM) to superferromagetism (SFM). Zero-field-cooled (ZFC) and field-cooled (FC) curves were obtained and long chain NP assemblies displayed ferromagnetism at the temperature ranging from 10 K to 400 K. Time-dependent remanent magnetic moment curves also indicated that the long chain structure had better thermal stability due to the strong exchange coupling.

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“…An ultimate state in the magnetic transitions is the formation of superferromagnetic entities at high concentration of nanoparticles. The formation of superferromagnetic chain like entities has been observed both in ordered as well as disordered arrangement of magnetic particles in a matrix through a systematic increase of concentration/density [11][12][13][14][15][16][17][18][19] . In all the studies reported so far the major emphasis has been to control the absolute size and size distribution of the nanoparticles such that they remain in a single state of magnetic order and probe the static and dynamic behavior of this state.…”

Section: Introductionmentioning

confidence: 99%

Interparticle interactions mediated superspin glass to superferromagnetic transition in Ni-bacterial cellulose aerogel nanocomposites

Thiruvengadam

Vitta

2016

Journal of Applied Physics

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The interparticle interactions in a magnetic nanocomposite play a dominant role in controlling the phase transitions -superparamagnetic to superspinglass to superferromagnetic. These interactions can be tuned by controlling the size and number density of nanoparticles. Aerogel composites, 0.3 Ni-BC and 0.7 Ni-BC, consisting of Ni nanoparticles distributed in bacterial cellulose have been used as model systems to study the effect of interparticle interactions with increasing fraction of Ni in the composite. Contrary to conventional approach, the size of Ni nanoparticles is not controlled and was allowed to form naturally in the bacterial cellulose template. The structural characterization using x-ray diffraction and electron microscopies indicates the presence of only Ni and cellulose with no other phases. Thermogravimetric analysis shows that the Ni content in the two aerogels is 78 % and 83.8 % respectively. The uncontrolled growth of Ni in cellulose matrix results in the formation of nanoparticles with 3 different size distributions -< 10 nm particles mainly distributed along the length of fibrils, 50 nm particles present in the intermediate spaces between the fibrils and > 100 nm particles present in voids formed by the reticulate structure. The magnetic behavior of these composites as a function of temperature, magnetic field and frequency shows that different magnetic states can be accessed at different temperatures. At room temperature the composites exhibit a weakly ferromagnetic behavior with a coercivity of 40 Oe which increases to 160 Oe at 10 K. The magnetization at both the temperatures however is found to be non-saturating even at fields as high as 20 kOe. The transition from weakly ferromagnetic state at room temperature to a superferromagnetic state at low temperatures is mediated via a superspinglass state at intermediate temperatures.Both the superspinglass state and the superferromagnetic state are found to be sustained by the interparticle interactions aided by the presence of small nanoparticles along the length of cellulose fibres. A temperature dependent microstructural model has been developed combining the structural and magnetic results obtained from the two composite aerogels. *satish.vitta@iitb.ac.in

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Superferromagnetism in chain-like Fe@SiO2 nanoparticle ensembles

Cited by 30 publications

References 41 publications

Enhanced Collective Magnetic Properties Induced by the Controlled Assembly of Iron Oxide Nanoparticles in Chains

Enhanced Collective Magnetic Properties Induced by the Controlled Assembly of Iron Oxide Nanoparticles in Chains

Magnetic properties of cubic FeCo nanoparticles with anisotropic long chain structure

Interparticle interactions mediated superspin glass to superferromagnetic transition in Ni-bacterial cellulose aerogel nanocomposites

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