Microstructural, Electrical-, Magneto-Transport Properties of Grain Size Modulated Nanocrystalline Nd 0.67 Sr 0.33 MnO 3
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1118-K05-03
Microstructural, Electrical-, Magneto-Transport Properties of Grain Size Modulated Nanocrystalline Nd0.67Sr0.33MnO3 CMR Manganites S. Paul and T. K. Nath Magnetism and Magnetic Materials Laboratory, Department of Physics and Meteorology Indian Institute of Technology, Kharagpur: 721302, West Bengal, India
ABSTRACT We have investigated the effect of nanometric grain sizes on Microstructural, electrical-, magneto-transport and magnetic behaviors in nanocrystalline Nd0.67Sr0.33MnO3 CMR manganites. Three nanocrystalline powders of Nd0.67Sr0.33MnO3 were synthesized through chemical route “Pyrophoric Reaction Process” and calcined for 5 hrs at calcinations temperature (TCal = 650o C, 750o C, and 850o C). XRD patterns indicate that all the synthesized powders have pseudo-cubic perovskite structure without any secondary impurity phase. Using Debye Scherrer formula we calculated the crystallites size for three nanocrystalline Nd0.67Sr0.33MnO3 powders (~ 30, 40, and 54 nm for TCal = 650o C, 750o C, and 850o C respectively). TEM micrographs show that the average particle sizes are in nanometric regime (φ ~ 30-50 nm). In AC susceptibility and resistivity measurement we observed that there is an almost constant Curie temperature (TC) has value around 240 K and gradual decrease of metal-insulator transition temperature (TP) (from 200-129 K) with decrease of TCal. The magneto resistance of ultra fine nanoparticles increases with grain sizes. Highest magnetoresistance observed ~ 24 for Nd0.67Sr0.33MnO3 with TCal = 850o C. Experimental results revels, the effect of nanometric grain sizes has an important impact in magnetic properties and magneto-transport behaviors. INTRODUCTION Recently manganese perovskites of the form Re1-xAexMnO3 [where, Re=La, Nd, Pr, etc. trivalent rare-earth ions and Ae=Sr, Ca, Ba etc. divalent alkaline-earth ions] are attracted much attention to intense research due to their colossal magnetoresistive behavior both in pure and applied physics [1]. Those materials are very useful in the development of magnetic and magneto-resistive devices (having potential application in next generation digital recording, magnetic data storage and sensing devices) [2]. A huge numbers of studies on colossal magnetoresistive (CMR) materials have been carried out in case of single crystal [3], thin film [4], and ceramic [5] (La0.7Sr0.3MnO3) etc to search correct model to explain their magnetic, electrical- and magneto-transport properties and its possible application. Many theories have been proposed to explain the CMR effect, such as double exchange (DE) [6], phase separation combined with percolation [7], polaronic effects [8] etc. Number of investigation of grain size effect (in the nanometric regimes) on electrical, magnetic and magneto-transport properties of La1-xAexMnO3
have been published [9-12]. In this paper, we reported a detailed study of effect of nanometric grain size of chemically prepared Nd0.67Sr0.33MnO3 on microstructural, electrical and magnetotransport properties.
EXPERIMENTAL
Synthesis of N
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