Spin dynamics and criteria for onset of exchange bias in superspin glass Fe/<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>γ</mml:mi></mml:math>-Fe<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>2</mml:mn></mml:msub></mml:math>O<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>3</mml:mn></mml:msub></mml:math>core-shell nanoparticles

Chandra, Sayan; Khurshid, Hafsa; Li, Wanfeng; Hadjipanayis, G. C.; Phan, Manh‐Huong; Srikanth, H.

doi:10.1103/physrevb.86.014426

Cited by 72 publications

(82 citation statements)

References 58 publications

(60 reference statements)

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“…27,28 It is also observed that the M s value of bare (y = 0) nanoparticles is greater than coated nanoparticles which is due to their large average crystallite size of uncoated nanoparticles as compared to coated nanoparticles. 29 Similar phenomenon was also reported for NiFe 2 O 4 and CoFe 2 O 4 ferrite nanoparticles. 30,31 The variation of coercivity (H c ) with SiO 2 concentration depends upon the anisotropy of nanoparticles.…”

Section: -4 Kamran Et Alsupporting

confidence: 66%

Role of SiO2 coating in multiferroic CoCr2O4 nanoparticles

et al. 2017

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Effect of silica (SiO2) coating concentration on structural and magnetic properties of multiferroic cobalt chromite (CoCr2O4) nanoparticles have been studied. The nanoparticles with average crystallite size in the range 19 to 28 nm were synthesised by sol-gel method. X-ray diffraction (XRD) analysis has verified the composition of single-phase cubic normal spinel structure of CoCr2O4 nanoparticles. The average crystallite size and cell parameter decreased with increasing SiO2 concentration. TEM image revealed that the shape of nanoparticles was non-spherical. Zero field cooled/field cooled (ZFC/FC) curves revealed that nanoparticles underwent a transition from paramagnetic (PM) state to collinear short-range ferrimagnetic (FiM) state, and this PM–FiM transition temperature decreased from 101 to 95 K with increasing SiO2 concentration or decreasing crystallite size. A conical spin state at Ts = 27 K was also observed for all the samples which decreased with decreasing average crystallite size. Low temperature lock-in transition was also observed in these nanoparticles at 12 K for uncoated nanoparticles which slightly shifted towards low temperature with decreasing average crystallite size. Saturation magnetization (Ms) showed decreasing trend with increasing SiO2 concentration, which was due to decrease in average crystallite size of nanoparticles and enhanced surface disorder in smaller nanoparticles. The temperature dependent AC-susceptibility also showed the decrease in the transition temperature (Tc), broadening of the Tc peak and decrease in magnetization with increasing SiO2 concentration or decreasing average crystallite size. In summary, the concentration of SiO2 has significantly affected the structural and magnetic properties of CoCr2O4 nanoparticles.

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Section: -4 Kamran Et Alsupporting

confidence: 66%

Role of SiO2 coating in multiferroic CoCr2O4 nanoparticles

et al. 2017

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“…However, we have observed the enhancement of ÀDS M in an applied magnetic field as low as 0.2 T, a magnetic field that is often insufficient to align the magnetic moments of disordering surface spins. 28 Moreover, the alignment of surface spins in high magnetic fields cannot be solely the cause for the observed large ÀDS M ($10 J/kg K) obtained in our sample. The MCE at low temperatures for these clathrate-nanocrystals, therefore, must be associated with the intrinsic magnetic transitions of the system.…”

Section: Resultsmentioning

confidence: 93%

Enhanced cryogenic magnetocaloric effect in Eu8Ga16Ge30 clathrate nanocrystals

Biswas

Chandra

Stefanoski

et al. 2015

Journal of Applied Physics

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Articles you may be interested inLarge magnetocaloric effects over a wide temperature range in MnCo1−xZnxGe J. Appl. Phys. 113, 17A922 (2013); 10.1063/1.4798339 We observe an enhanced magnetic entropy change (ÀDS M ) at cryogenic temperatures (T < 20 K) in Eu 8 Ga 16 Ge 30 clathrate (type-I) nanocrystals prepared by a ball milling method. With reduction in the crystal size to 15 nm, ÀDS M is enhanced at low temperatures, reaching the highest value ($10 J/kg K) at 5 K for a field change of 5 T. For all samples investigated, there is a cross-over temperature ($25 K) in ÀDS M (T) above which ÀDS M decreases with crystal size, opposite to that observed at low temperatures. A careful analysis of the magnetic and magnetocaloric data reveals that as the crystal size decreases the magnetic interaction between Eu 2þ ions on the Eu2 site governing the primary ferromagnetic transition at $35 K becomes gradually weaker, in effect, altering the interaction between Eu 2þ ions occupying the Eu1 and Eu2 sites responsible for the secondary ferromagnetic transition at 15 K. As a result, we have observed a strong change in magnetization and the enhancement of ÀDS M at low temperature. V C 2015 AIP Publishing LLC.

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“…8 A vast majority of the latter field of research has been approached by analyzing the family of 3d -transition metal compounds in the form (mostly) of Fe-oxides and Fe NPs forming different nanostructures. [9][10][11] Their production routes are various, and the basic characterization is relatively easy to achieve. From a different perspective, most of the work has been concentrated on ferromagnetic (FM), or ferrimagnetic (FiM) NPs, whereas the work with antiferromagnetic (AFM) NPs provides a valuable information of the particle shell and surface interface.…”

Section: -7mentioning

confidence: 99%

Magnetic phase diagram of superantiferromagnetic TbCu₂nanoparticles

Echevarria-Bonet

Rojas

Espeso

et al. 2015

J. Phys.: Condens. Matter

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The structural state and static and dynamic magnetic properties of TbCu2 nanoparticles are reported. The nanoparticles were produced by mechanical milling under inert atmosphere with low milling times ≤ 15 hours. The randomly dispersed nanoparticles as detected by TEM retain the bulk symmetry with an orthorhombic Imma lattice and Tb and Cu in 4c positions. Rietveld refinements confirm that the milling produces a controlled reduction of particle sizes reaching down to ≃ 6 nm and an increase of the microstrain ≃ 0.6 %. The DC-susceptibility shows a reduction of the Néel transition (from 49 K to 43 K) and a progressive increase of the spin glass peak (from 9 to 15 K) in the zero field cooled magnetization with size reduction. The exchange anisotropy is very weak (bias field of ≃ 30 Oe) and is due to the presence of a disordered (thin) shell coupled to the antiferromagnetic core. The dynamic susceptibility evidences a critical slowing down in the spin disordered state with a tendency to increase of zv and β exponents when the size becomes smaller (zv ≃ 6.6 and β ≃ 0.85). A Rietveld analysis of neutron diffraction patterns 1.8 ≤ T ≤ 60 K including the magnetic structure determination reveals that there is a reduction of the expected moment (≃ 80 %) which must be connected to the presence of the disordered particle shell. The core magnetic structure retains the bulk antiferromagnetic arrangement. The overall interpretation is based on a superantiferromagnetic behavior which at low temperatures coexists with a canting of surface moments. We propose a novel magnetic phase diagram as a function of the particle size.

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Spin dynamics and criteria for onset of exchange bias in superspin glass Fe/γ-Fe2O3core-shell nanoparticles

Cited by 72 publications

References 58 publications

Role of SiO2 coating in multiferroic CoCr2O4 nanoparticles

Role of SiO2 coating in multiferroic CoCr2O4 nanoparticles

Enhanced cryogenic magnetocaloric effect in Eu8Ga16Ge30 clathrate nanocrystals

Magnetic phase diagram of superantiferromagnetic TbCu₂nanoparticles

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Spin dynamics and criteria for onset of exchange bias in superspin glass Fe/γ-Fe2O3core-shell nanoparticles

Cited by 72 publications

References 58 publications

Role of SiO2 coating in multiferroic CoCr2O4 nanoparticles

Role of SiO2 coating in multiferroic CoCr2O4 nanoparticles

Enhanced cryogenic magnetocaloric effect in Eu8Ga16Ge30 clathrate nanocrystals

Magnetic phase diagram of superantiferromagnetic TbCu2nanoparticles

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Magnetic phase diagram of superantiferromagnetic TbCu₂nanoparticles