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R Nirmala
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R Nirmala
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R Nirmala
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Nirmala, R.
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11 results
Now showing 1 - 10 of 11
- PublicationElectrical and magnetotransport properties of canted antiferromagnet Dy5Si2Ge2(01-01-2002)
; ; ; ;Morozkin, A. V. ;Chu, Z. ;Yelon, W. B. ;Malik, S. K. ;Prasad, V.Subramanyam, S. V.Since the giant magnetocaloric effect is encountered in a ferromagnetic Gd5Si2Ge2 alloy near room temperature it is considered as a suitable material for magnetic refrigerator applications. Also a commensurate structural transition occurs at the magnetic transition temperature and there is a good correlation between the crystal structure and magnetic properties. Such observations have triggered numerous experimental studies on similar rare earth alloys and compounds. We have synthesized its Dy- analogue, namely, Dy5Si2Ge2 and have characterized it by means of room temperature X-ray diffraction, ac magnetic susceptibility (15 K-300 K), electrical resistivity (at zero field and at 6 T), thermoelectric power (15 K-300 K) and neutron diffraction (at 300 K and 9.2 K) experiments. - PublicationMagnetic and magnetocaloric properties of the intermetallic compound ErCu2(19-05-2017)
;Rajivgandhi, R. ;Chelvane, J. AroutPolycrystalline ErCu2 compound has been prepared by arc melting in inert atmosphere and its magnetic and magnetocaloric properties have been studied. ErCu2 orders antiferromagnetically at TN ~ 11 K. A field induced metamagnetic transition is observed in a field of ~8.5 kOe at 5 K which leads to saturation in magnetization to a value of max 8.4 μB/f.u. The maximum isothermal magnetic entropy change, -ΔSmmax, value of this compound is obtained as 14.9 J/kg K for 50 kOe field change. Corresponding refrigeration capacity and relative cooling power values are 334 J/kg and 412 J/kg, respectively. These values are higher than that for HoCu2 and DyCu2 compounds because the temperature dependent isothermal magnetic entropy change curve of this ErCu2 compound is considerably broader. - PublicationMagnetocaloric effect in mixed rare earth manganite Gd0.5Dy0.5MnO3(04-05-2020)
;Behera, P. SuchismitaSingle phase, polycrystalline mixed rare earth manganite Gd0.5Dy0.5MnO3 (orthorhombic, Pbnm) has been prepared by solid state reaction. Magnetization vs temperature data measured in 100 Oe field shows a weak cusp and a tendency to order around 5 K. Paramagnetic susceptibility shows Curie-Weiss behaviour. Magnetocaloric effect (MCE) has been estimated in terms of isothermal magnetic entropy change (ΔSm). The maximum value of ΔSm is about -13.4 Jkg-1K-1 at 8 K for a field change of 70 kOe. - PublicationEffect of Mn on the magnetic and electrical properties of Ho 0.85Tb0.15Fe2(01-12-2006)
;Chelvane, J. Arout; ;Kumar, N. Harish; Malik, S. - PublicationMagnetic, magnetocaloric and electrical transport properties of electron-doped manganite Eu0.15Ca0.85MnO3(05-11-2020)
;Thangavel, KavipriyaIn the present work, magnetic and magnetocaloric properties of Eu0.15Ca0.85MnO3 oxide have been studied. The sample crystallizes in orthorhombic crystal structure (space group Pnma, no. 62) at 300 K and undergoes a paramagnetic to antiferromagnetic transition at ~115 K (TN). The magnetization value at 5 K in field of 70 kOe is only 0.11 μB/f.u. Thermal hysteresis in low field magnetization data around TN suggests a first order transition. Metamagnetic behaviour is observed at temperatures immediately below TN. This suggests the presence of competing magnetic interactions. Isothermal magnetic entropy change is calculated from magnetization-field data and its maximum value is ~ +10 Jkg-1K-1 at 107.5 K for a field change of 70 kOe. Inverse magnetocaloric effect and the magnetic moment value in the ordered state reveal the robust antiferromagnetism in this manganite. In addition, the electrical resistivity shows semiconducting behaviour and increases strongly at low temperatures. - PublicationElectrical and magnetotransport properties of canted antiferromagnet Dy5Si2Ge2(01-12-2002)
; ; ; ;Morozkin, Alex V. ;Chu, Zili ;Yelon, W. B. ;Malik, S. K. ;Prasad, V.Subramanyam, S. V.The electrical and magnetotransport properties of canted antiferromagnet Dy5Si2Ge2 are discussed. The DC electrical resistivity measurements confirm the magnetic crossover by a strong change of slope. The resistivity drops abruptly below TN as the spin disorder contribution vanishes. The application of magnetic field suppresses the TN by about 6 K thereby emphasizing the nature of the magnetic order to be antiferromagnetic. - PublicationOn the magnetism and magnetocaloric effect of electron-doped manganite Er0.15Ca0.85MnO3(10-04-2018)
;Naskar, Moumita ;Ghorai, Sagar ;Prabhakar, S. ;Rajivgandhi, R. ;Rayaprol, S. ;Nigam, A. K. ;Quezado, S. ;Malik, S. K.Magnetic and magnetocaloric properties of polycrystalline electron-doped manganite Er0.15Ca0.85MnO3 are studied. Room temperature powder neutron diffraction data confirm that the sample is in single phase with orthorhombic crystal structure (Space group Pnma, No. 62). This sample orders antiferromagnetically at ∼112 K (TN). At temperatures below TN, a metamagnetic transition is observed in magnetization-field (M-H) isotherms. Using M-H data, isothermal magnetic entropy change (ΔSm) is estimated. The magnetocaloric effect changes from negative to positive as Er0.15Ca0.85MnO3 undergoes paramagnetic to antiferromagnetic transition at TN. Within the antiferromagnetically ordered state, sign changes again due to the metamagnetic transition. - PublicationEffect of particle size on electrical and magnetotransport properties of manganite nanoparticles(01-01-2005)
;Krishnamoorthy, C.; ;Sethupati, K.; Malik, S. K. - PublicationMagnetocaloric effect in a multicomponent laves phase intermetallic compound Gd0.2Tb0.2Dy0.2HO0.2Er0.2Al2(05-11-2020)
;Jesla, P. K. ;Arout Chelvane, J. ;Nigam, A. K.A multicomponent Laves phase intermetallic compound Gd0.2Tb0.2Dy0.2Ho0.2Er0.2Al2 has been synthesized and characterized by means of magnetization measurements. The Gd0.2Tb0.2Dy0.2Ho0.2Er0.2Al2 crystallizes in MgCu2-type cubic structure (space group Fd-3m) at 300 K. Magnetization data reveal a paramagnetic to ferromagnetic transition at about 80 K (Tc). Paramagnetic susceptibility obeys Curie-Weiss law. Magnetization vs field (M-H) data at 2 K indicate saturation behaviour with negligible hysteresis. The saturation magnetization value at 2 K is ~8.6 μB/fu. Magnetocaloric effect has been estimated using M-H data obtained in the neighbourhood of Tc. Maximum isothermal magnetic entropy change is found to be ~ -11 Jkg-1K-1 at 72.5 K for a field change of 50 kOe and a large refrigeration capacity of about 750 J/kg is obtained. Observation of normal magnetocaloric effect and the saturated magnetic moment value at 2 K suggest long range ferromagnetic order in this multicomponent system. - PublicationMagnetic and magnetocaloric properties of rare earth intermetallic compound DyCoNi(01-12-2012)
;Mondal, Rajib ;Chelvane, J. AroutMagnetic and magnetocaloric properties of Laves phase rare earth intermetallic compound DyCoNi (cubic, MgCu2-type) have been studied. Magnetization data reveal a ferromagnetic transition at ∼68 K (T C). Magnetocaloric effect has been estimated in terms isothermal magnetic entropy change using field dependent magnetization data taken at various temperatures around TC. The maximum isothermal magnetic entropy change (-ΔSm) is found to be ∼ 15.5 J/kg-K near TC for 7 T field change. © 2012 American Institute of Physics.