Giant exchange bias in MnPd/Co bilayers

 A systematic study of exchange bias in MnPd/Co bilayers has been carried out, where the dependences of exchange bias, unidirectional anisotropy constant and coercivity on the thicknesses of MnPd and Co layers were investigated. A huge unidirectional anisotropy constant, J(K) = 2.5 erg/cm(2) was observed, which is in reasonable agreement with the theoretical prediction based on the model by Meiklejohn and Bean. The angular dependences of exchange bias field and coercivity have also been examined showing that both exchange bias and coercivity follow 1/ cos alpha rule. (c) 2007 Elsevier B.V. All rights reserved. http://repository.vnu.edu.vn/handle/VNU_123/31126

Manganese perovskites for room temperature magnetic refrigeration applications

 We found the large magnetocaloric effect (MCE) in La0.6Ca0.3Pb0.1MnO3 (sample No. 1), La0.7Ca0.2Pb0.1MnO3 (sample No. 2), and La0.7Ca0.1Pb0.2MnO3 (sample No. 3) perovskites, which were prepared by a conventional ceramic method. For a magnetic field change of 13.5 kOe, the magnetic entropy change (Delta S-M) reached values of 2.55, 2.53 and 3.72 J/kg K for samples Nos. 1, 2 and 3, respectively. Interestingly, the large Delta S-M was found to occur around 300 K for all samples investigated, which allows magnetic refrigeration at room temperature. These perovskites have the large magnetic entropy changes induced by low magnetic field change, which is beneficial for the household application of active magnetic refrigerant (AMR) materials. (C) 2007 Elsevier B.V. All rights reserved. http://repository.vnu.edu.vn/handle/VNU_123/31120

Longitudinal Hall effect in Terfecohan thin films with perpendicular magnetic anisotropy

 Longitudinal extraordinary Hall Effect (LEHE) of magnetic Tb( Fe0.55Co0.45)(1.5) (known as Terfecohan) thin films with perpendicular magnetic anisotropy has been investigated as a function of both the intensity of applied magnetic fields and the angle alpha between the applied field and film normal directions. The Hall voltage loops exhibit a parallelogram shape, which is almost similar to those of the perpendicular magnetization. The high-field Hall voltage susceptibility is positive at alpha = 0. Its value decreases with increasing alpha and changes in sign at alpha(m) 20 degrees, which is considered as the easy magnetizable direction of the film. This finding is comparable with those obtained from the magnetization, magnetic force microscopy (MFM) and conversion electron Mossbauer spectra (CEMS) measurements. The obtained LEHE behaviors are rather promising for applications such as magnetic recording heads and magnetic field detectors, where a large output signal is required at low magnetic fields. (c) 2007 Elsevier B.V. All rights reserved.. Mời bạn đọc xem tại đây: http://repository.vnu.edu.vn/handle/VNU_123/31096

Magnetization and magnetostriction process in spring-magnet TbFeCo/Fe multilayers with variable TbFeCo thickness

 Different natures of the magnetization reversal are studied by means of magnetization and magnetostriction measurements for magnetostrictive "spring-magnet'' multilayers of TbFeCo/Fe with a. fixed Fe layer thickness of 10 nm and variable TbFeCo layer thickness of 12, 16 and 20 nm. In such multilayered systems, magnetization reversal occurs at different coercive fields for each layer related to formation of the domain wall at interfaces. The results show that at low temperatures, transition from the ferromagnetic saturation state (with domain walls) to the ferrimagnetic transient saturation state (without domain walls) takes place by the reversal of the magnetic moments in the high-magnetization Fe layers. This process is governed by large magnetic anisotropy of the TbFeCo layer. Increasing temperature, this anisotropy decreases and transition results from the reversal of magnetic moments in the small magnetization TbFeCo layers. Formation of the domain wall at interfaces is clearly evidenced by the negative contribution to the parallel magnetostriction. (c) 2007 Elsevier B.V. All rights reserved. Mời bạn đọc xem tại đây: http://repository.vnu.edu.vn/handle/VNU_123/31064

Study of the determination of inorganic arsenic species by CE with capacitively coupled contactless conductivity detection

 The determination of arsenic(III) and arsenic(V), as inorganic arsenite and arsenate, was, investigated by CE with capacitively coupled contactless conductivity detection (CE-C-4 D). It was found necessary to determine the two inorganic arsenic species separately employing two different electrolyte systems. Electrolyte solutions consisting of 50 mM CAPS/2 MM L-arginine (Arg) (pH 9.0) and of 45 mM acetic acid (pH 3.2) were used for arsenic(III) and arsenic(V) determinations, respectively. Detection limits of 0.29 and 0.15 mu M were achieved for As(III) and As(V), respectively by using large-volume injection to maximize the sensitivity. The analysis of contaminated well water samples from Vietnam is demonstrated.
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New fully portable instrument for the versatile determination of cations and anions by capillary electrophoresis with contactless conductivity detection

 A new portable capillary electrophoresis instrument with capacitively coupled contactless conductivity detection was developed and optimized for the sensitive field measurements of ionic compounds in environmental samples. It is powered by batteries and the high voltage modules are capable of delivering up to 15 kV at either polarity for more than one working day. Inorganic cations and anions, including ions of heavy metals and arsenate, could be determined with detection limits in the range from about 0.2 to 1 mu M. The instrument was field tested in a remote region of Tasmania and nitrite and ammonium could be determined on-site at concentrations as low as 10 ppb in presence of other common inorganic ions at concentrations which were 2 to 3 orders of magnitude higher.
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Continuous parallel-iterated RKN-type PC methods for nonstiff IVPs

 This paper investigates parallel predictor-corrector (PC) iteration schemes based on direct collocation Runge-Kutta-Nystrom (RKN) corrector methods with continuous output formulas for solving nonstiff initial-value problems (IVPs) for systems of special T second-order differential equations y ''(t) = f(t, y(t)). Consequently, the resulting parallel-iterated RKN-type PC methods are provided with continuous output formulas. The continuous numerical approximations are also used for predicting the stage values in the PC iteration processes. In this way, we obtain parallel PC methods with continuous output formulas and high-order predictors. Applications of the resulting parallel PC methods to a few widely-used test problems reveal that these new parallel PC methods are much more efficient when compared with the parallel-iterated RKN (PIRKN) methods and the sequential ODEX2 and DOPRIN codes from the literature. (c) 2006 IMACS. Published by Elsevier B.V. All rights reserved.
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