JOURNAL OF NANO- AND ELECTRONIC PHYSICS ǴȁРǻАǹ ǻАǻǼ- ȀА dzǹdzǸȀРǼǻǻǼǦ ȂǥǵǶǸǶ Vol. 7 No 1, 01001(5pp) (2015) Том 7 № 1, 01001(5cc) (2015) 2077-6772/2015/7(1)01001(5) 01001-1  2015 Sumy State University Effect of Electron Beam Irradiation on Structural, Electrical and Thermo-electric Power of La0.8Sr0.2MnO3 Ashok Rao 1,* , J. Benedict Christopher 1 , Ganesh Sanjeev 2 , G.S. Okram 3 1 Department of Physics, Manipal Institute of Technology, Manipal University, Manipal-576104, India 2 Microtron Centre, Mangalore University, Mangalagangotri – 574199, DK, Karnataka, India 3 UGC-DAE Consortium for Scientific Research, University Campus, Indore-452017, India (Received 05 December 2014; published online 25 March 2015) In this communication, we are reporting the effect of electron beam (e-beam) irradiation on thermoelec- tric properties of La0.8Sr0.2MnO3 manganites. The samples were prepared using solid state reaction tech- nique. It is observed that the lattice volume increases with increase in dosage of e-beam. With irradiation an increase in resistivity is observed. For small irradiation dosage, we first observe a decreases in metal- insulator transition temperature TMI; thereafter TMI increases with further increase in dosage of irradia- tion. Both, the resistivity data and thermo-electric power data demonstrate that small polaron hopping model is valid in high temperature region. Keywords: Solid state reaction technique, Electrical resistivity, Thermoelectric power. PACS numbers: 81.20.Ev, 72.15.Eb, 72.15.Jf * ashokanu_rao@rediffmail.com 1. INTRODUCTION Ever since the discovery of colossal magneto- resistance effect (CMR) and large magneto-caloric ef- fect in rare earth manganite of the form RE1 – xAxMnO3 (RE is a rare-earth element, A is a divalent alkaline element), immense work has been done on the electri- cal, magnetic and thermal properties of these materials [1-9]. The primary aim of such studies is to understand the physics behind these properties and to explore pos- sibilities of using them in various applications [10]. These manganites show numerous interesting proper- ties like metal-insulator transition, and paramagnetic- ferromagnetic transition. Over the decades, energetic ion-beams and electron beams have been used as a vi- tal tool for modification of materials [11, 12]. Extensive work seems to have been done on various ion irradia- tions. Chattopadhyay et al. [13] have shown that La 3+ ion irradiation creates disorder in La0.7Ca0.3MnO3 (LCMO) manganite sample and as a result of this an increase in room temperature resistivity is observed. Ravi Kumar et al. [14] has reported the influence of swift heavy ion irradiation on transport properties of thin films of LCMO system and have demonstrated that TC decreases with increase in fluence of the beam. On the other hand they have reported that the resistiv- ity of the films increases with fluence value. Kataria et al. [15] have reported interesting results which indicate that thickness of films of LPMO plays important role and they have demonstrated that for small thickness of 150 nm, irradiated films have lower resistivity than pristine films of same thickness. However, for films of thickness 150 nm and above, an increase in resistivity is seen when the samples are irradiated. La1 – xSrxMnO3 (LSMO) in particular has attracted lot of attention as they are considered to be prototypical and reference ma- terials [16, 17]. They are promising materials since they show ferromagnetic-paramagnetic transition and also exhibit significant magneto-resistance (MR) value [18, 19] which essentially make them promising candi- dates for applications. Sahasrabudhe et al. [20] have done a detailed investigation on the effect of heavy ion irradiation on the surface morphology of highly orient- ed thin films of LSMO and concluded using XRD that irradiation induces strain in the films. Less work seems to have been done on effect of electron beam irradiation on manganites. Samoilenko et al. [21] have demonos- trated that when thin films of LSMO are irradiated by KrF laser emitting in the UV range, the metallic phase of the film is observed to increase. Pallecchi et al. [22] have investigated the effect of focused ion beam (Ga ion) on LSMO films and have shown that resistivity increas- es with increases in dosage of irradiation. To the best of our knowledge, no work seems to have been done electron beam irradiation on LSMO system. Keeping this in mind, we have investigated the effect of electron beam irradiation on structural, elec- trical and thermo-electric properties of La0.8Sr0.2MnO3 compounds. We have focused the present studies on thermoelectric power as it is sensitive to the nature of charge carriers. The Seebeck coefficient (S) of mang- nites exhibits a complex behavior indicating both posi- tive and negative signs which depends on temperature as well as on the nature and degree of substitution. In the low temperature regime S is related to the changes in electronic structure and scattering processes, where- as in the insulating region S provides information on energy dependent parameters which follow small po- laron hopping mechanism. Thus it would be interesting to see the effect of electron beam irradiation on ther- moelectric power of La0.8Sr0.2MnO3 compounds. 2. EXPERIMENTAL In this work, single phase polycrystalline stronti- um-substituted lanthanum manganite (La0.8Sr0.2MnO3) compounds were prepared by conventional solid state reaction technique. Stoichiometric amounts of lantha-