Effects of Mn-site doping on the magnetocaloric properties of La0.62Bi0.05Ca0.33Mn1-xRuxO3 manganite system

This study reports the effects of Ru element doping in La0.62Bi0.05Ca0.33Mn1-xRuxO3 (x=0.0, 0.1 and 0.2) manganite compounds on the magnetocaloric (MC) properties of materials obtained by solid-state method. XRD analysis showed that the samples crystallized in orthorhombic structure (with Pnma space group). The magnetic phase transition temperatures of the samples were determined from the thermomagnetic curves as 221 K for x = 0.0 sample and 215 and 206 K for x = 0.1 and x = 0.2 samples, respectively, under 100 Oe applied field. Arrott plots confirm that the type of magnetic phase transition is second-order phase transition. The -∆S_M^max values were calculated as 7.55, 3.51 and 2.69 J/kgK for x = 0.0, 0.1 and 0.2 samples, respectively. Relative cooling power (RCP) values decrease with Ru doping. It was concluded that the Ru additive had an effect on reducing the transition temperatures and magnetic entropy change values of the samples

HTc süperiletkenlerinin fiziksel özelliklerinin teorisi

TEZ2942Tez (Yüksek Lisans) -- Çukurova Üniversitesi, Adana, 1998.Kaynakça (s. 62-68) var.v, 69 s. ; 30 cm.…Bu çalışma Ç.Ü. Bilimsel Araştırma Projeleri Birimi Tarafından Desteklenmiştir. Proje No: FBE. 97. YL. 150

Bscco süperiletkenlerine yapılan katkıların yapısal ve fiziksel özelliklerine etkileri

TEZ5455Tez (Doktora) -- Çukurova Üniversitesi, Adana, 2005.Kaynakça (s. 143-146) var.ix, 146 s. ; 30 cm.

La0.67Ba0.33MnO3’ deki Manyetokalorik Etkinin Doğrudan ve Dolaylı Ölçümlerden Belirlenmesi

Bu çalışmada, sol-jel yöntemi ile üretilen La0.67Ba0.33MnO3 perovskit bileşiğindeki manyetokalorik etki özelliği incelenmiştir. 50 Oe uygulanan manyetik alan altında sıcaklığa bağlı manyetizasyon ölçümlerinden örneğin sıcaklığın artışıyla birlikte ferromanyetik-paramanyetik faz geçişi gösterdiği gözlenmiştir. Örneğin ?Tad değeri alan artarken ve azalırken doğrudan ölçülmüştür. Sonuçlar ?Tad'nin her iki durumda da aynıdeğeri göstermesinden manyetokalorik etkinin tersinir olduğunu göstermektedirIn this study, we investigated magnetocaloric properties of the perovskite compound La0.67Ba0.33MnO3 synthesized by sol-gel technique. The temperature dependent magnetization measurements at 50Oe applied magnetic field showed that the sample displays a ferromagnetic-paramagnetic transition with increasing temperature. ?Tad of the sample was measured both on increasing and decreasing fields directly. The results indicate that the magnetocaloric effect is largely reversible due to showing the same ?Tad for both case

A theoretical model for the non-linear susceptibility of the antiferromagnetic systems

In this study, we have developed a general theoretical model, based upon the simple mean field model of Neel, for the non-linear response of an antiferromagnetic system. The results indicate that the odd order derivatives, $(d^{2n + 1}m_a)_0 = (-d^{2n + 1}m_b)_0$, where n=1,2,3......, will diverge and the even order derivatives, $(d^{2n}m_a)_0 = (d^{2n}m_b)0$ will vanish due to the symmetry of two sublattices, -a'' and -b'', forming the antiferromagnet. This model also supports our experimental results performed on two antiferromagnetic samples, namely, $Cs_2MnCl_4.2H_2O$ and $MnCl_2.4H_2O$ [1].In this study, we have developed a general theoretical model, based upon the simple mean field model of Neel, for the non-linear response of an antiferromagnetic system. The results indicate that the odd order derivatives, $(d^{2n + 1}m_a)_0 = (-d^{2n + 1}m_b)_0$, where n=1,2,3......, will diverge and the even order derivatives, $(d^{2n}m_a)_0 = (d^{2n}m_b)0$ will vanish due to the symmetry of two sublattices, -a'' and -b'', forming the antiferromagnet. This model also supports our experimental results performed on two antiferromagnetic samples, namely, $Cs_2MnCl_4.2H_2O$ and $MnCl_2.4H_2O$ [1]

Structural, magnetic and magnetocaloric properties of (La1-xSmx)(0.85)K0.15MnO3 (x=0.0, 0.1, 0.2 and 0.3) perovskite manganites

WOS: 000413175300170We have investigated effect of Sm ion substitution on structural, magnetic and magnetocaloric properties of solgel synthesized (La(1-x)Smx)(0.85)K0.15MnO3 (x = 0.0, 0.1, 0.2 and 0.3) perovskite manganites. X-ray diffraction analyses confirm that samples crystallize with rhombohedral symmetry in the R3c space group. The temperature dependence of magnetization measurements shows a clear ferromagnetic (FM)-paramagnetic (PM) phase transition with increasing temperature, and magnetic phase transition temperature (T-c) decreases with increasing Sm concentration. For Sm concentrations (x = 0.0, 0.1, 0.2 and 0.3), magnetic field dependence of the maximum magnetic entropy change (-Delta S-M(max)) are determined up to 5 T to be 7.32, 3.37, 3.28 and 2.70 J kg(-1) K-1, respectively. These experimental values are also in good agreement with the calculation of the magnetic entropy change using Landau theory.Research Fund of Cukurova University, Adana, TurkeyCukurova University [FEF2012D12, FBA-2015-5028]This work is supported by the Research Fund of Cukurova University, Adana, Turkey, under grant contracts no. FEF2012D12 and FBA-2015-5028

Effect of Pr-substitution on the structural, magnetic and magnetocaloric properties of (La1-xPrx)(0.67)Pb0.33MnO3 (0.0 <= x <= 0.3) manganites

WOS: 000412712900151The effects of the substitution of La3+ by smaller rare-earth ion Pr3+ on the structural, magnetic and magnetocaloric properties of (La1-xPrx)(0.67)Pb0.33MnO3 (0.0 <= x <= 0.3) compounds prepared by sol-gel method have been investigated. X-ray diffraction (XRD) showed that samples crystallize in the orthorhombic perovskite structure with Pnma space group. Thermomagnetic measurements indicate that all the samples exhibit a magnetic transition from ferromagnetic to paramagnetic phase with increasing temperature. Curie temperature, T-C, systematically decreases from 358 K for x = 0.0 to 330 K for x = 0.3 as the average ionic radius of the A-site elements. The magnetic entropy change, Delta S-M; was calculated from the isothermal magnetization measurements as a function of applied magnetic field at several temperatures around T-C. The maximum of magnetic entropy change was found to be 4.43, 3.08, 3.33 and 2.97 Jkg(-1)K(-1) for x = 0.0, 0.1, 0.2 and 0.3, respectively, for a magnetic field change of 4.8 T. The field dependence of the magnetic entropy change is also analyzed and can be expressed by a power law Delta S-m(max) = alpha(mu H-0)(n), where the magnetic-ordering parameter is n = 0.59, 0.62, 0.62 and 0.65 at 4.8 T applied magnetic field for x = 0.0, 0.1, 0.2 and 0.3 samples, respectively. Arrott plots and universal behavior of the scaled entropy change curves show that all samples display a second order magnetic phase transition. (C) 2017 Elsevier B.V. All rights reserved.Cukurova University, Adana, TurkeyCukurova University [FEF2010D4, FBA-2015-5028]; Deutsche ForschungsgemeinschaftGerman Research Foundation (DFG) [SPP1599]This work was supported by the Research Fund of Cukurova University, Adana, Turkey, under grant contracts no. FEF2010D4, no. FBA-2015-5028 and Deutsche Forschungsgemeinschaft SPP1599. The authors acknowledge the Turkish Council of Higher Education for supporting Selda Kilic Cetin's visit to Duisburg-Essen University

Impact of small Er rare earth element substitution on magnetocaloric properties of (La0.9Er0.1)(0.6)PB0.33MnO3 perovskite

WOS: 000487930600066In this work, the effect of Er substitution on the magnetic and magnetocaloric properties has been studied for (La0.9Er0.1)(0.6)PB0.33MnO3 perovskite synthesized by the sol-gel procedure. Magnetization measurements performed as a function of both temperature and magnetic field in order to determine magnetic and magnetocaloric properties. The temperature dependence of magnetization measured under 5 mT magnetic field indicate that sample exhibits ferromagnetic (FM) to paramagnetic (PM) transition with increasing temperature. The Curie temperature (T-C) decreases with Er-doping from 358 K for La0.67Pb0.33MnO3 to 349 K. From the isothermal magnetization measurements taken up to 5T around the T-C in 3 K intervals, the magnetic entropy change (Delta S-M) values of the sample have been determined for different magnetic fields. The Delta S(M)(max )value has been calculated as 0.98, 1.73, 2.33, 2.85 and 3.23 Jkg(-1)K(-1) for 1, 2, 3, 4 and 4.8 T, respectively. The type of magnetic phase transition has been determined as the second order from the slope of Arrott plots. (C) 2019 Elsevier B.V. All rights reserved.Research Fund of Cukurova University, Adana, TurkeyCukurova University [FEF2010D4]This work is supported by the Research Fund of Cukurova University, Adana, Turkey, under grant contracts no. FEF2010D4

Microstructural and magnetic properties of A(x):Zn1-xO (A=Mn, Gd and Mn/Gd) nanocrystals

WOS: 000368724800003We report the microstructural and magnetic properties of transition (3d) and rare earth (4f) metal substituted into the A(x):Zn1-xO (A=Mn, Gd and Mn/Gd) nanocrystal samples synthesized by solgel method. The structural properties and morphology of all samples have been analysed using X-ray diffraction (XRD) method and scanning electron microscopy. The impurity phase in the XRD patterns for all samples is not seen, except (Mn/Gd):ZnO sample where a very weak secondary phase of Gd2O3 is observed. Due to the large mismatch of the ionic radii between Mn2+ and Gd3+ ions, the strain inside the matrix increases, unlike the crystallite size decreases with the substitution of Mn and Gd into ZnO system. A couple of additional vibration modes due to the dopant have been observed in Raman spectrum. The magnetic properties have been studied by vibrating sample magnetometer. The magnetic hysteresis shows that Mn:ZnO and Gd:ZnO have soft ferromagnetic (FM) behaviour, whereas (Mn/Gd):ZnO has strong FM behaviour at room temperature (RT). The enhancement of ferromagnetism (FM) in (Mn/Gd):ZnO sample might be related to short-range FM coupling between Mn2+ and Gd3+ ions via defects potential and/or strain-induced FM coupling due to the expansion lattice by doping. The experimental results indicate that RTFM can be achieved by co-substitution of 3d and 4f metals in ZnO which can be used in spintronics applications.Cukurova University (Adana/Turkey)Cukurova University [FBA-2015-4464, FBA-2015-5028, FEF2013D31]This work was supported by Cukurova University (Adana/Turkey) [project number FBA-2015-4464]; [project number FBA-2015-5028]; [project number FEF2013D31]