Solid State Science and Technology, Vol. 20, No 1& 2 (2012) 1-10

ISSN 0128-7389




L.S. Ewe1,, A.Jemat1, W. N. Voon1 and K.P.Lim2


1College of Foundation and General Studies, Universiti Tenaga Nasional,

Kampus Putrajaya, Jalan IKRAM-UNITEN,

43000 Kajang, Selangor, Malaysia

2Department of Physics, Faculty of Science, Universiti Putra Malaysia,

43300 UPM Serdang, Selangor, Malaysia

*Corresponding author:



A systematic study on Nd0.68Sr0.32MnO3 manganites has been undertaken, primarily to

understand the influence of varying grain size on the structural, electrical resistivity and

magneto transport properties at the insulating and metallic regions. The materials were

prepared by the solid state reaction method at sintering temperature 1170oC, 1270oC

and 1350oC. The XRD patterns show all samples have a single phase with

orthorhombic structure. SEM images show a linear relationship between sintering

temperature and grain size. The insulator metal transition temperatures, Tim were

determined and remained nearly constant (~ 200 K) for samples sintered at 1270 oC and

1350oC. While for sample sintered at 1170 oC, Tim is found around 180 K. The

resistivity data fits well with equations ρ = ρo + ρ2T2 and ρ = ρo + ρ2.5T2.5 in metallic

(ferromagnetic) region. At high temperature (T>Tim) insulating (paramagnetic) region,

small polaron hopping and variable range hopping models were used to compute the

density of states at Fermi level N(EF) and the activation energy (Ea) of the electrons.


Keywords: magnetotransport; grain size; activation energy



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