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Nanto, D.,Zhang Peng,Yong-Yeal Song,Seong-Cho Yu,Telegin, S.,Elochina, L.,Telegin, A. IEEE 2012 IEEE transactions on magnetics Vol.48 No.11
<P>Non-stoichiometric Nd<SUB>0.5</SUB>Sr<SUB>0.5</SUB>MnO<SUB>3</SUB> (NSMO) single crystalline has been grown by the floating zone method. Their magnetic properties, magnetocaloric effect (MCE) and refrigerant capacity (<I>RC</I>) at near both first- and second-order phase transitions were investigated. The NSMO system goes through an antiferomagnetic charge-ordered transition at <I>T</I><SUB>CO</SUB> ~ 152 K followed by a ferromagnetic to paramagnetic transition at <I>T</I><SUB>C</SUB> ~ 272 K. The transition region spread over a broader temperature range at the <I>T</I><SUB>C</SUB> but it had a narrower temperature range at the <I>T</I><SUB>CO</SUB>. The maximum magnetic entropy change Δ<I>S</I><SUB>max</SUB> gives about 1.65 J · kg<SUP>-1</SUP> · K<SUP>-1</SUP> at the first order magnetic transition and -1.13 J · kg<SUP>-1</SUP> · K<SUP>-1</SUP> at the second order magnetic transition, respectively. <I>RC</I> is obtained and it shows much higher value about 34.85 J/kg at <I>T</I><SUB>C</SUB> than the <I>RC</I> 19.06 J/kg at <I>T</I><SUB>CO</SUB>. The slight non-stoichiometric NSMO single crystalline system raises the Curie temperature around 30 K towards room temperature without degradation of the <I>RC</I> and temperature span corresponding to the full width at half maximum of Δ<I>S</I><SUB>max</SUB>(Δ<I>T</I><SUB>FWHM</SUB>) compared to pure single crystalline NSMO system.</P>
Thanh, Tran Dang,Xuan Hau, Kieu,Huyen Yen, Pham Duc,Manh, T. V.,Yu, S. C.,Phan, T. L.,Telegin, A.,Telegin, S.,Naumov, S. IEEE 2018 IEEE transactions on magnetics Vol.54 No.11
<P>In this paper, we present a detailed analysis on the critical behavior of La<SUB>1.2</SUB>Sr<SUB>1.8</SUB>Mn<SUB>2</SUB>O<SUB>7</SUB> single crystal via isothermal magnetization measured at different temperatures around the paramagnetic–ferromagnetic phase transition at <TEX>$T_{C} = 85$</TEX> K. Using the Landau–Lifshitz coefficients, the Arrott plots ( <TEX>$H/M = a(T) + b(T)M^{2}$</TEX>) of sample have been analyzed. It showed that a(T) changed from positive to negative values at different temperatures in the field ranges of <TEX>$H = 0$</TEX>–10, 10–30, and 30–50 kOe, indicating that the critical behavior could not be described with a single model under different applied fields. Through the modified Arrott plots method, the Kouvel–Fisher method, and the critical isotherm analysis, we determined the values of the critical exponents for La<SUB>1.2</SUB>Sr<SUB>1.8</SUB>Mn<SUB>2</SUB>O<SUB>7</SUB> around its magnetic phase transition over different magnetic field ranges. The critical exponent <TEX>$\beta $</TEX> value is found to be 0.501, 0.417, and 0.371 under field ranges of <TEX>$H = 0$</TEX>–10, 10–30, and 30–50 kOe, respectively. This means that the <TEX>$\beta $</TEX> value depends strongly on the strength of the applied field, shifting from the value approaching that of the mean field model ( <TEX>$\beta = 0.5$</TEX>) to the 3-D-Heisenbeg model ( <TEX>$\beta = 0.365$</TEX>). Meanwhile, its <TEX>$\gamma $</TEX> value is quite stable ( <TEX>$\gamma =0.973$</TEX>–1.074), almost independent on the choice of field fitting range. In addition, using the reduced temperature <TEX>$\varepsilon = (T-T_{C}$</TEX>)/ <TEX>$T_{C}$</TEX> and the obtained critical exponents, almost <TEX>$M(H, T$</TEX>) data measured near <TEX>$T_{C}$</TEX> obey the scaling equation <TEX>$M(H, \varepsilon) = \varepsilon ^{\boldsymbol {\beta }}f_{\pm }(H/\varepsilon ^{\boldsymbol {\beta +\gamma }}$</TEX>), where <TEX>$f_{+}$</TEX> and <TEX>$f_{-}$</TEX> are regular analytic functions corresponding to data at <TEX>$T > T_{C}$</TEX> and <TEX>$T < T_{C}$</TEX>, respectively.</P>
Nanto, Dwi,Seong-Cho Yu,Suhk-Kun Oh,Chebotaev, Nikolay,Telegin, Andrey IEEE 2014 IEEE transactions on magnetics Vol.50 No.4
<P>Manganite perovskite with A-site deficiency has been synthesized by a solid-state reaction technique. Our work does not support a general view that A-site deficiency gives a decrease on Curie temperature. The Curie temperature of (La<SUB>0.8</SUB>Ca<SUB>0.2</SUB>)<SUB>0.975</SUB>MnO<SUB>3.01</SUB> is 188 K with maximum entropy change -ΔSM <SUB>max</SUB> = 1.6 J·kg<SUP>-1</SUP>·K<SUP>-1</SUP> and refrigerant capacity (RC) of 27 J/kg under an applied field of 10 kOe. The nonstoichiometric (La<SUB>0.8</SUB>Ca<SUB>0.2</SUB>)<SUB>0.975</SUB>MnO<SUB>3.01</SUB> may offer a wider temperature span of ~240% compared with those nanocrystalline La<SUB>0.8</SUB>Ca<SUB>0.2</SUB>MnO<SUB>3.01</SUB> that have similar RC, which has been reported by others.</P>
Magnetic and Magnetocaloric Properties of Ca0.97La0.03MnO3 Manganites
Gong, G. D.,Hu, P. F.,Li, Y.,Kim, D. H.,Liu, C. L.,Phan, T. L.,Ho, T. A.,Yu, S. C.,Telegin, A.,Naumov, S. V. Springer Science + Business Media 2016 Journal of electronic materials Vol.45 No.7
<P>In spite of many previous studies on electron-doped CaMnO3 perovskite manganites, detailed investigations into the influence of low-doping concentrations on their magnetic and magnetocaloric (MC) properties have not been carried out yet. Additionally, there is still the lack of the comparison between single-crystal (SC) and polycrystalline (PC) materials. Dealing with these problems, we prepared orthorhombic Ca0.97La0.03MnO3 SC and PC samples. Magnetization measurements versus the temperature and magnetic field revealed remarkable differences in the magnetic property, particularly around the antiferromagnetic/ferromagnetic-paramagnetic phase-transition region. The analyses of the magnetization versus magnetic field, M(H), data indicated a weak MC effect with magnetic-entropy changes less than 0.1 J kg(-1) K-1 for an applied field interval H = 10 kOe because ferromagnetic interactions between Mn3+ and Mn4+ ions are insignificant. The differences in the magnetic and MC properties of the SC and PC samples are ascribed to the effects of grain boundary, magnetic anisotropy, and nonstoichiometry in oxygen.</P>