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Tuning of the Curie Temperature in La1-xSrxMn1-yTiyO₃
N. X. Phuc,N. T. Hieu,N. T. H. Le,D. H. Manh,N. A. Tuan,L. V. Hong,L. T. C. Tuong 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5
Magnetic nanoparticles of La₁-xSrxMn₁-yTiyO₃ were prepared by using a sol-gel method, followed by annealing at various elevated temperatures. We found that the Curie temperature of the manganite nanoparticles could easily be tuned (from TC ~ 90 ℃ down to ~20 ℃) by substitution of nonmagnetic Ti⁴+ ions (from y = 0 to 7 %) for Mn. A comparison showed that the titanium substitution approach had advantages such as the phase transition being sharper and the magnetization remaining higher than in the case of the earlier known way of TC reduction by decreasing the Sr content from the optimal value of x = 0.3. The new features seem to make La1..xSrxMn₁..yTiyO₃ nanoparticles promising for hyperthermia application. Magnetic nanoparticles of La₁-xSrxMn₁-yTiyO₃ were prepared by using a sol-gel method, followed by annealing at various elevated temperatures. We found that the Curie temperature of the manganite nanoparticles could easily be tuned (from TC ~ 90 ℃ down to ~20 ℃) by substitution of nonmagnetic Ti⁴+ ions (from y = 0 to 7 %) for Mn. A comparison showed that the titanium substitution approach had advantages such as the phase transition being sharper and the magnetization remaining higher than in the case of the earlier known way of TC reduction by decreasing the Sr content from the optimal value of x = 0.3. The new features seem to make La1..xSrxMn₁..yTiyO₃ nanoparticles promising for hyperthermia application.
QUADRUPLY-IMAGED QUASARS: SOME GENERAL FEATURES
Tuan-Anh, P.,Thai, T.T.,Tuan, N.A.,Darriulat, P.,Diep, P.N.,Hoai, D.T.,Ngoc, N.B.,Nhung, P.T.,Phuong, N.T. The Korean Astronomical Society 2020 Journal of The Korean Astronomical Society Vol.53 No.6
Gravitational lensing of point sources located inside the lens caustic is known to produce four images in a configuration closely related to the source position. We study this relation in the particular case of a sample of quadruply-imaged quasars observed by the Hubble Space Telescope. Strong correlations between the parameters defining the image configuration are revealed. The relation between the image configuration and the source position is studied. Some simple features of the selected data sample are exposed and commented upon. In particular, evidence is found for the selected sample to be biased in favor of large magnification systems. While having no direct impact on practical analyses of specific systems, our results have pedagogical value and deepen our understanding of the mechanism of gravitational lensing.
Grain Refinement of Al-Mg-Sc Alloy by Ultrasonic Treatment
N. Q. Tuan,H. Puga,J. Barbosa,A. M. P. Pinto 대한금속·재료학회 2015 METALS AND MATERIALS International Vol.21 No.1
In foundry practice, ultrasonic treatment has been used as an efficient technique to achieve grain refinementin aluminium and magnesium alloys. This article shows the strong effect of pouring temperature and ultrasonictreatment at various temperatures on the grain refinement of Al-1 wt% Mg-0.3 wt% Sc alloy. Without ultrasonictreatment, a fine grain structure was obtained at the pouring temperature of 700 °C. The average grain sizesharply decreases from 487 ± 20 to 103 ± 2 μm when the pouring temperature decreases from 800 to 700 °C. Ultrasonic vibration proved to be a potential grain refinement technique with a wide range of pouring temperature. A microstructure with very fine and homogeneous grains was obtained by applying ultrasonic treatmentto the melt at the temperature range between 700 and 740 °C, before pouring. Cavitation-enhanced heterogeneousnucleation is the mechanism proposed to explain grain refinement by ultrasound in this alloy. Moreover,ultrasonic treatment of the melt was found to lead to cast samples with hardness values similar to those obtainedin samples submitted to precipitation hardening, suggesting that ultrasonic treatment can avoid carrying out heattreatment of cast parts.
Anomalous magnetoimpedance in Co–Fe–Al–O thin films
Tuan, L. A.,Phan, M. H.,Ha, N. D.,Kim, C. G.,Kim, C. O.,Yu, S. C. Wiley - VCH Verlag GmbH & Co. KGaA 2007 Physica Status Solidi C Vol.4 No.12
<P>The high-frequency giant magnetoimpedance (GMI) effect in a Co<SUB>47.5</SUB>Fe<SUB>21.9</SUB>Al<SUB>17.2</SUB>O<SUB>15.2</SUB> thin film was systematically investigated. In the frequency range of 100–500 MHz, GMI profiles showed a double-peak characteristic, reflecting an evident existence of the transverse magnetic anisotropy in the film, which coincided with the magnetization data. Interestingly, there was an anomalous transformation in the GMI profile from “positive” to “negative” and this was associated with the complex phase transformation of permeability. The GMI ratio decreased with decreasing film-thickness, due to an increase of the electrical resistivity and a decrease of the magnetic softness. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>
Ultrasoft magnetic properties of Co–Fe–Hf–O nanocomposite films
Ha, N. D.,Phan, M. H.,Tuan, L. A.,Phan, T. L.,Kim, C. G.,Kim, C. O.,Yu, S. C. WILEY-VCH Verlag 2007 Physica status solidi. PSS. A, Applications and ma Vol.204 No.12
<P>This paper reports on the excellent high-frequency magnetic performance of Co–Fe–Hf–O thin films, which were deposited on Si(100) substrates by the oxygen reactive rf-sputtering method. It was shown that the films possessed not only high electrical resistivity but also large saturation magnetization and hard-axis anisotropy field. Among the compositions investigated, Co<SUB>19.35</SUB>Fe<SUB>53.28</SUB>Hf<SUB>7.92</SUB>O<SUB>19.35</SUB> exhibited the ultrasoft magnetic properties of high saturation magnetization, 4πM<SUB>s</SUB> ∼19.86 kG, and low coercivity, H<SUB>c</SUB> ∼1.5 Oe. The magnetic permeability remained almost constant up to 3 GHz and reached a maximum at the ferromagnetic resonant frequency of 4.024 GHz. These properties of this film together with a high electrical resistivity of 3569 μΩcm make it ideal for producing micromagnetic devices for high-frequency applications. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>