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R. Martínez-Snchez J. A. Matutes-Aquino O. Ayala-Valenzuela S. D. De la Torre 《Physica B: Condensed Matter》2002,320(1-4):285-287
An amorphous phase containing traces of non-transformed Co and Ti powders was obtained by mechanical alloying nominal compositions of Co67Ti33 and Co50Ti50 in a high-energy ball-mill. These alloys were prepared from elemental powders of Co and Ti. The heat treatment of Co67Ti33 at 573, 873 and 1173 K crystallized nanoparticles of Co2Ti and Co3Ti compounds, while the same treatments conducted on Co50Ti50 resulted in the formation of Co2Ti and CoTi nanoparticles. The saturation magnetizations reached a maximum value in the amorphous state and they decreased when the temperatures of the heat treatment rose. Demagnetizing interparticle interaction effects were estimated through hysteresis loops and initial magnetization curves using the Fourier technique. 相似文献
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Bauer ED Altarawneh MM Tobash PH Gofryk K Ayala-Valenzuela OE Mitchell JN McDonald RD Mielke CH Ronning F Griveau JC Colineau E Eloirdi R Caciuffo R Scott BL Janka O Kauzlarich SM Thompson JD 《J Phys Condens Matter》2012,24(5):052206
The physical properties of the first In analog of the PuMGa(5) (M = Co, Rh) family of superconductors, PuCoIn(5), are reported. With its unit cell volume being 28% larger than that of PuCoGa(5), the characteristic spin-fluctuation energy scale of PuCoIn(5) is three to four times smaller than that of PuCoGa(5), which suggests that the Pu 5f electrons are in a more localized state relative to PuCoGa(5). This raises the possibility that the high superconducting transition temperature T(c) = 18.5 K of PuCoGa(5) stems from the proximity to a valence instability, while the superconductivity at T(c) = 2.5 K of PuCoIn(5) is mediated by antiferromagnetic spin fluctuations associated with a quantum critical point. 相似文献
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Goddard PA Manson JL Singleton J Franke I Lancaster T Steele AJ Blundell SJ Baines C Pratt FL McDonald RD Ayala-Valenzuela OE Corbey JF Southerland HI Sengupta P Schlueter JA 《Physical review letters》2012,108(7):077208
Gaining control of the building blocks of magnetic materials and thereby achieving particular characteristics will make possible the design and growth of bespoke magnetic devices. While progress in the synthesis of molecular materials, and especially coordination polymers, represents a significant step towards this goal, the ability to tune the magnetic interactions within a particular framework remains in its infancy. Here we demonstrate a chemical method which achieves dimensionality selection via preferential inhibition of the magnetic exchange in an S=1/2 antiferromagnet along one crystal direction, switching the system from being quasi-two- to quasi-one-dimensional while effectively maintaining the nearest-neighbor coupling strength. 相似文献
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Oscar Ayala-Valenzuela Paul C. Fannin Rebeca Betancourt-Galindo Oliverio Rodríguez-Fernández José Matutes-Aquino 《Journal of magnetism and magnetic materials》2007
Magnetic nanoparticles with different compositions (CoxFe3−xO4, 0?x?0.1) were synthesized from metal salts using a coprecipitation technique to produce magnetic fluids following a peptization technique. The liquid carrier was the hydrocarbon Isopar M and the surfactant was oleic acid. The colloidal-sized ferrimagnetic nanoparticles produced were found to be superparamagnetic. Measurements of the complex magnetic susceptibility were carried out to evaluate the resonant frequency fres, the anisotropy constant K, and anisotropy field HA. fres was found to be a linear function of the cobalt content of the magnetic nanoparticles over the range of cobalt content studied. 相似文献
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S. Ponce-Castañeda J.R. Martínez S. Palomares-Sánchez Facundo Ruiz O. Ayala-Valenzuela J.A. Matutes-Aquino 《Journal of Sol-Gel Science and Technology》2003,27(3):247-254
A detailed infrared spectroscopy analysis in the 2500 to 3800 cm–1 region has been used to study the formation of species in samples of iron oxides embedded in silica xerogel matrix. We report the presence of , , and forms of iron oxyhydroxides as intermediate species in the formation of -Fe2O3, -Fe2O3 and -Fe2O3 starting from three different iron precursors: iron nitrate, iron chloride and nanometric Fe particles prepared by chemical reduction. Our results show that under thermal dehydration and forms of iron oxyhydroxides transform into hematite and maghemite, respectively, whereas the form transform to the -Fe2O3 without going through an intermediate iron oxide phase. 相似文献
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