Size effects in the magnetic behaviour of TbAl<sub>2</sub>milled alloys

Rojas, D.P.; Barquı́n, L. Fernández; Fernández, J. Rodrı́guez; Espeso, J.I.; Sal, J.C. Gómez

doi:10.1088/0953-8984/19/18/186214

Cited by 27 publications

(49 citation statements)

References 43 publications

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“…A progressive broadening and reduction in the intensity of the peaks, commonly related to both a decrease in the particle size ͑D͒ and an increase in the lattice strain ͑͒, is observed. 9 The Rietveld refinement of the x-ray diffraction data shows a decrease in the particle size down to 10 nm and an increase in the lattice strain up to 0.4% for 120 h of milling time. The refinement was carried out using the Pm3m space group and the Thompson-Cox-Hastings pseudo-Voigt function for the peak profile, similar to that employed in the analysis of TbAl 2 milled alloys.…”

Section: Resultsmentioning

confidence: 96%

“…17 This maximum is virtually absent in the 20 h milled alloy and practically disappears for 120 h of milling time samples ͑probably as a result of the disorder increase͒, which is induced by the milling process. [4][5][6][7][8][9] Regarding the high-temperature maximum ͑usually associated with the Kondo temperature in these IV systems͒, 18 there is a slight decrease ͑1%-2%͒ in the position directly affected by the mentioned Curie-Weiss behavior of the Yb 2 O 3 . However, the absolute value of the magnetic susceptibility decreases 14%, 25%, and 30% for 20, 70, and 120 h of milling time, respectively, which is a significant sign of an increasing presence of Yb 2+ contribution.…”

Section: B DC Magnetic Susceptibilitymentioning

confidence: 81%

“…The refinement was carried out using the Pm3m space group and the Thompson-Cox-Hastings pseudo-Voigt function for the peak profile, similar to that employed in the analysis of TbAl 2 milled alloys. 9 The size of the particles and the lattice strain as function of the milling time for the YbAl 3 series is depicted in Fig. 2.…”

Section: Resultsmentioning

confidence: 99%

“…[4][5][6][7][8] More recently, a study of the magnetic properties of TbAl 2 milled alloys has revealed that not only disorder but also size effects are important in crucial understanding of the magnetic behavior, with a pronounced variation of coercivity with the grain size. 9 The relevance of the extension of these studies of nanocrystalline particle systems to Ce and Yb intermetallics, the latter being known as strongly correlated electron materials, requires some understanding of how macroscopic properties in these systems become modified at the nanoscale. In this sense, results have been reported in Ce-Al ͑Ref.…”

Section: Introductionmentioning

confidence: 99%

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Reduction of the Yb valence inYbAl3nanoparticles

et al. 2008

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Measurements of specific heat, dc magnetic susceptibility, and Yb L II and L III x-ray absorption near-edge structure ͑XANES͒ and extended x-ray absorption fine structure ͑EXAFS͒ on YbAl 3 milled alloys are reported. X-ray diffraction patterns are consistent with a reduction in particle size down to 10 nm and an increase in the lattice strain up to 0.4% for 120 h of milling time. A decrease in the mean valence from 2.86 for the unmilled alloy to 2.70 for 120 h milled YbAl 3 is obtained from the analysis of XANES spectra. From the analysis of spectra in the EXAFS region, an increase in the mean-square disorder of neighbor distance with milling time is detected in good agreement with the results of x-ray diffraction. Size effects strongly influence the magnetic and thermal properties. The value for the maximum of the magnetic susceptibility decreases around 30% for 120 h milled alloy and an excess specific heat, with a peak around 40 K in the milled samples, is derived. These changes in the physical properties along the milled YbAl 3 alloys are associated with the reduction in particle size. Such a reduction leads to the existence of a large number of Yb 2+ atoms at the surface with respect to the bulk affecting the overall electronic state.

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Section: Resultsmentioning

confidence: 96%

Section: B DC Magnetic Susceptibilitymentioning

confidence: 81%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Reduction of the Yb valence inYbAl3nanoparticles

et al. 2008

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“…Recently, there are consistent investigations on MNPs of rare Earth (R)-based alloys (Zhou and Bakker 1995;Li et al 2013;Morales et al 2004;Wang et al 2007;de Paula et al 2016;Sánchez-Valdés et al 2014;Rojas et al 2007;EchevarriaBonet et al 2013;Echevarria-Bonet et al 2015). These studies are much less widespread than the usual investigations of Fe, Ni, Co oxide MNPs (Tartaj et al 2003;Estrader et al 2013;RinaldiMontes et al 2015), although some of these R-based alloys allow for technological transfer as permanent magnets or magnetocaloric materials (Wang et al 2007;de Paula et al 2016;Sánchez-Valdés et al 2014).…”

Section: Introductionmentioning

confidence: 99%

Surfactant-assisted production of TbCu2 nanoparticles

et al. 2017

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The production of surfactant-assisted metallic nanoparticles of TbCu 2 has been achieved by the combination of high-energy ball milling in tungsten carbide containers and the use of oleic acid (C 18 H 34 O 2 ) and heptane (C 7 H 16 ). The alloys were first produced in bulk pellets by arc melting and subsequently milled for only 2 and 5 h in oleic acid (15 and 30% mass weight). The powders consist of an ensemble of nanoparticles with a TbCu 2 lattice cell volume of ≈215 Å 3 , an average particle diameter between 9 and 12 nm and inhomogeneous lattice strain of 0.2-0.4%, as deduced from X-ray diffraction data. The nanometric sizes of the crystals with defined lattice planes are close to those obtained by transmission electron microscopy. Raman spectroscopy shows the existence of inelastic peaks between 1000 and 1650 cm −1 , a characteristic of C 18 H 34 O 2 . The magnetisation shows a peak at the antiferromagneticparamagnetic transition with Néel temperatures around 48 K (below that of bulk alloy) and a distinctive metamagnetic transition at 5 K up to 40 K. The CurieWeiss behaviour above the transition reveals effective Bohr magneton numbers (≈9.1-9.9 μ B ) which are close to what is expected for the free Tb 3+ ion using Hund's rules. The metamagnetic transition is slightly augmented with respect to the bulk value, reaching H = 24.5 kOe by the combined effect of the size reduction and the lattice strain increase and the increase of magnetic disorder. At low temperatures, there is irreversibility as a result of the existing magnetic disorder. The moment relaxation follows an Arrhenius model with uncompensated Tb moments, with activation energies between 295 and 326 K and pre-exponential factors between 10 −11 and 10 −13 s. The results are interpreted as a consequence of the existence of a diamagnetic surfactant which drastically decreases the magnetic coupling between interparticle moments.

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