Physical Mechanisms of Exchange Coupling Effects in Nanoparticulate Diluted Magnetic Oxides Obtained by Laser Pyrolysis

Kuncser, V.; Schinteie, G.; Kuncser, Andrei; Leca, Aurel; Scarisoreanu, M.; Morjan, I.; Filoti, G.

doi:10.1021/acs.jpcc.7b01500

Cited by 7 publications

(13 citation statements)

References 27 publications

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“…It is evident that the specific susceptibility in Figure 5C follows a paramagnetic C/T type dependence, with C the Curie constant and T the temperature. Here C = N A* μ 2 /3k B , where k B is the Boltzmann constant, μ is the magnetic moment of the magnetic center, and N A is the Avogadro number 72 …”

Section: Discussionmentioning

confidence: 54%

“…Finally, the specific magnetization from the hysteresis loop at 10 K in Figure 5D can be corrected also by the paramagnetic contribution (paramagnetic susceptibility multiplied with the applied field) resulting finally a saturated magnetic loop specific to only the ferromagnetic component. The ferromagnetic signal could be due to the defects from the glass network, which conduct to the diluted magnetic oxide behavior 72‐74 . From the saturation magnetization of the ferromagnetic component which equates the Avogadro number multiplied with the magnetic moment contributed to the ferromagnetic ordered phase, the value of the magnetic moment per molecule can be directly obtained.…”

Section: Discussionmentioning

confidence: 99%

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Synthesis and characterization of a titanium phosphate‐tellurite glass for Faraday rotators

et al. 2020

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This work is focused on investigation of thermal, structural, optical, magnetic, and magneto‐optical properties of novel titanium phosphate‐tellurite glass applied as Faraday rotators. The glass belonging to the system 35Li2O–10Al2O3–5TiO2–45P2O5–5TeO2 was prepared by a nonconventional wet route of raw materials processing, followed by melting‐quenching‐annealing steps. Some important physical properties of the investigated glass have been measured and calculated, providing knowledge related to glass compactness, electronic structure, glass forming capability, etc. XRD analysis evidenced an amorphous network structure of the investigated glass. The optical absorption in the Vis domain is mainly due to Ti3+ ions and Te2 clusters formed during the glass melting process. A relatively low optical absorption is noticed over 600 nm that activates a significant Faraday magneto‐optical effect. Photoluminescence bands in the blue, red, and infrared domains are observed, caused by Te2 clusters formed during the glass melting process. The magnetization in dependency on applied magnetic field reveals a complex behavior of the glass, depending on temperature. Thus, it is found a ferromagnetic behavior up to 2000 Oe, a paramagnetic component up to 40 000 Oe, followed by a diamagnetic one over 40 000 Oe. Faraday rotation angle and Verdet constant values in the visible domain are correlated with the reduced TeO2 content of the glass.

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Section: Discussionmentioning

confidence: 54%

Section: Discussionmentioning

confidence: 99%

Synthesis and characterization of a titanium phosphate‐tellurite glass for Faraday rotators

et al. 2020

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“…The negative slope was clearly lower in absolute value at 10 K, giving an indirect indication for an additional paramagnetic contribution of positive slope, which compensates partially for the decrease of magnetization at this temperature. The direct indication for the paramagnetic contribution can be observed from the strong increase of the magnetization at temperatures lower than 20 K (see inset of Figure 8 a) resembling closely to the typical paramagnetic C/T type dependence with C the Curie constant and T the temperature [ 36 ]. The diamagnetic susceptibility of the Te-5 glass can be calculated from the slope of the linear decrease of the magnetization at 300 K, where the paramagnetic contribution was negligible.…”

Section: Resultsmentioning

confidence: 89%

A New Zinc Phosphate-Tellurite Glass for Magneto-Optical Applications

et al. 2020

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This work investigates the structural, magnetic and magneto-optical properties of a new zinc phosphate-tellurite glass belonging to the 45ZnO-10Al2O3-40P2O5-5TeO2 system. The glass was prepared by a wet method of processing the starting reagents followed by suitable melting–stirring–quenching–annealing steps. Specific parameters such as density, average molecular mass, molar volume, oxygen packaging density, refractive index, molar refractivity, electronic polarizability, reflection loss, optical transmission, band gap and optical basicity have been reported together with thermal, magnetic and magneto-optical characteristics. Absorption bands appear in the blue and red visible region, while over 600 nm the glass becomes more transparent. FTIR and Raman spectra evidenced phosphate-tellurite vibration modes proving the P2O5 and TeO2 network forming role. Magnetic measurements reveal the diamagnetic character of the Te-doped glass with an additional weak ferromagnetic signal, specific to diluted ferromagnetic oxides. Positive Faraday rotation angle with monotonous decreasing value at increasing wavelength was evidenced from magneto-optical measurements. The final product is a composite material comprising of a non-crystalline vitreous phase and Te-based nanoclusters accompanied by oxygen vacancies. The metallic-like Te colloids are responsible for the dark reddish color of the glass whereas the accompanying oxygen vacancies might be responsible for the weak ferromagnetic signal persisting up to room temperature.

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“…(3) is not valid for these samples too. It is to be noted here that the exchange bias field is cancelled out at a temperature of 50 K, also known as the blocking temperature of exchange bias 31 , being marked in the following as T EB . Hence, samples A and A200 are representative cases of nanoparticulate systems with T EB < T B .…”

Section: Resultsmentioning

confidence: 97%

“…To note the specific negative shifts of the hysteresis loops in the case of samples A and A200C, better evidenced after cooling the samples in an applied field. This well-known behavior is due to the presence of unidirectional anisotropy in a nanometer size ferromagnetic-like phase interfaced to an antiferromagnetic-like phase [30][31][32] . Among the macroscopic effects of such interfacial interactions are: (1) the increased coercivity of the multi-phase system and (2) the above mentioned shift of the hysteresis loop, denoted as an exchange bias field.…”

Section: Resultsmentioning

confidence: 99%

Tuning structural and magnetic properties of Fe oxide nanoparticles by specific hydrogenation treatments

Greculeasa

Palade

Schinteie

et al. 2020

Sci Rep

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Structural and magnetic properties of Fe oxide nanoparticles prepared by laser pyrolysis and annealed in high pressure hydrogen atmosphere were investigated. The annealing treatments were performed at 200 °C (sample A200C) and 300 °C (sample A300C). The as prepared sample, A, consists of nanoparticles with ~ 4 nm mean particle size and contains C (~ 11 at.%), Fe and O. The Fe/O ratio is between γ-Fe2O3 and Fe3O4 stoichiometric ratios. A change in the oxidation state, crystallinity and particle size is evidenced for the nanoparticles in sample A200C. The Fe oxide nanoparticles are completely reduced in sample A300C to α-Fe single phase. The blocking temperature increases from 106 K in A to 110 K in A200C and above room temperature in A300C, where strong inter-particle interactions are evidenced. Magnetic parameters, of interest for applications, have been considerably varied by the specific hydrogenation treatments, in direct connection to the induced specific changes of particle size, crystallinity and phase composition. For the A and A200C samples, a field cooling dependent unidirectional anisotropy was observed especially at low temperatures, supporting the presence of nanoparticles with core–shell-like structures. Surprisingly high MS values, almost 50% higher than for bulk metallic Fe, were evidenced in sample A300C.

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Physical Mechanisms of Exchange Coupling Effects in Nanoparticulate Diluted Magnetic Oxides Obtained by Laser Pyrolysis

Cited by 7 publications

References 27 publications

Synthesis and characterization of a titanium phosphate‐tellurite glass for Faraday rotators

Synthesis and characterization of a titanium phosphate‐tellurite glass for Faraday rotators

A New Zinc Phosphate-Tellurite Glass for Magneto-Optical Applications

Tuning structural and magnetic properties of Fe oxide nanoparticles by specific hydrogenation treatments

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