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Papers by Sankaranarayanan Venkataraman

Journal of the Physical Society of Japan, 2000

INTERMAG Asia 2005. Digests of the IEEE International Magnetics Conference, 2005., 2005

A systematic study of the particle size effect on electrical, magnetic and colossal magnetoresist... more A systematic study of the particle size effect on electrical, magnetic and colossal magnetoresistance of nanocrystalline Nd0.7Sr0.3MnO3 sample was carried out. Samples were synthesised by citrate auto-ignition method. The resulting precursors were then calcined for 3 h at 700, 800 and 900°C to get different particle sizes. To measure electrical resistivity and magnetoresistance, pellets were sintered and quenched to room

INTERMAG Asia 2005. Digests of the IEEE International Magnetics Conference, 2005., 2005

ABSTRACT

Solid State Communications, 1990

Physica C: Superconductivity, 1989

... B 37 (1988) 611. [4] Nigel Goldenfield, PD Olmsted, TA Friedman and DM Ginsberg, Solid State ... more ... B 37 (1988) 611. [4] Nigel Goldenfield, PD Olmsted, TA Friedman and DM Ginsberg, Solid State Commun. 65 (1988) 465. ... Lett. 53 (1988) 414. [ 14] A. Sequeira, H. Rajagopal, IK Gopalakrishnan, PVPSS Sastry, GM Phatek, JV Yakhmi and RM Iyer, Physica C 156 (1988) 599. ...

Physica B: Condensed Matter, 2000

Preliminary results of AC magnetic susceptibility, DC electrical resistivity and thermopower meas... more Preliminary results of AC magnetic susceptibility, DC electrical resistivity and thermopower measurements on the new ternary compound Gd2Mn3Ge5 in the temperature range 15–300 K are reported. It is a ferromagnet at room temperature and the onset of ferromagnetism is observed around 236 K whereas reentrant ferromagnetism occurs near 88 K. The successive magnetic transitions are attributed to the layered structure of the compound.

Journal of Physics and Chemistry of Solids, 2008

Journal of Nanoparticle Research, 2006

Nanocrystalline samples with an average particle size of 40 and 52 nm have been synthesized by ci... more Nanocrystalline samples with an average particle size of 40 and 52 nm have been synthesized by citrate-complex auto-ignition method. Magnetic properties of the samples show para- to ferromagnetic transition at around 135 K. The electron magnetic resonance (EMR) study on these samples indicates the presence of coexistence of two magnetic phases below 290 K. Electrical resistivity follows variable range hopping (VRH) mechanism in the paramagnetic regime. The magnetoresistance (MR) data has been analysed by spin dependent hopping between the localized spin clusters together with the phase-separation phenomenon. These clusters are assumed to be formed by distribution of canted spins and defects all over the nanoparticle. In addition, the hopping barrier depends on the magnetic moment orientation of the clusters. The magnetic moments of the clusters are narrowly oriented in ferro- and are randomly oriented in paramagnetic phase. The ferromagnetic phase contributes to the total MR at low applied magnetic fields whereas the paramagnetic phase contributes at relatively high fields in both the samples. The average cluster size in ferromagnetic phase is bigger than that in paramagnetic phase. It is also observed that the cluster size, in ferromagnetic phase, in 52 nm sample is bigger than that in the 40 nm sample. However, the average cluster size in paramagnetic phase is almost same in both the samples.

Journal of Magnetism and Magnetic Materials, 2006

We have studied the effect of Ar annealing on the electrical and magnetic transport properties of... more We have studied the effect of Ar annealing on the electrical and magnetic transport properties of Pr 0.7 Sr 0.3 MnO 3 manganite. It is observed that, with increase in the annealing time there is a progressive decrease in T C and, resistivity, as functions of temperature become ...

Journal of Applied Physics, 2004

... 348, L1 (2003). 7 R. Nirmala, V. Sankaranarayanan, K. Sethupathi, AV Morozkin, T. Geethakumar... more ... 348, L1 (2003). 7 R. Nirmala, V. Sankaranarayanan, K. Sethupathi, AV Morozkin, T. Geethakumary, and Y. Hariharan, Pramana, J. Phys. 58, 1101 (2002). ... 283, 54 (1999). 9 A. Verniere, V. Klosek, R. Welter, G. Venturini, O. Isnard, and B. Mala-man, J. Magn. Magn. Mater. ...

Journal of Applied Physics, 2010

ABSTRACT Polycrystalline sample of La2CoMnO6 has been synthesized by sol-gel technique. The powde... more ABSTRACT Polycrystalline sample of La2CoMnO6 has been synthesized by sol-gel technique. The powder x-ray diffraction data confirm the single phase nature of the sample. This compound has monoclinic crystal structure (space group P21/n) at room temperature. The temperature dependence of magnetization in low field shows considerable variation between zero-field-cooled and field-cooled magnetization curve below ~210 K (TC) and it follows Curie-Weiss law in the paramagnetic region. The hysteresis loop at 5 K indicates a coercive field of ~6 kOe and remnant magnetization of ~2.32 muB/f.u. The temperature dependence of the resistivity data shows semiconductorlike behavior in the temperature range of 5-350 K and follows variable range hopping conduction mechanism in the temperature range 215-350 K. A colossal magnetoresistance of ~80% is observed at 5 K in an applied field of 80 kOe and MR has a negative sign.

Journal of Applied Physics, 2011

Magnetoresistance and magnetocaloric effect of a double perovskite oxide PrSrMnCoO6 (cubic, Fm3m)... more Magnetoresistance and magnetocaloric effect of a double perovskite oxide PrSrMnCoO6 (cubic, Fm3m) has been studied in fields up to 7 T. This compound is semiconductor-like and its electrical resistivity increases by 5 orders while going from 300 to 50 K. Giant magnetoresistance of ~40% is observed at 200 K in 7 T field. PrSrMnCoO6 orders ferromagnetically at ~150 K and