Multiple magnetic transitions and magnetocaloric effect in hydrothermally synthesized single crystalline La 0.5 Sr 0.5 M
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Multiple magnetic transitions and magnetocaloric effect in hydrothermally synthesized single crystalline La0.5Sr0.5MnO3 nanowires Sayan Chandra 1, Anis Biswas 1, Subarna Datta2, Barnali Ghosh 2, A.K. Raychaudhuri 2, M.H. Phan 1 and H. Srikanth 1* 1 Department of Physics, University of South Florida, Tampa, FL 33620, USA 2 Unit for Nanoscience, S N Bose National Centre for Basic Science, Kolkata 700098, India
ABSTRACT We have successfully prepared La0.5Sr0.5MnO3 nanowires using a novel hydrothermal synthesis process and studied their magnetic and magnetocaloric properties. The system exhibits an inverse magnetocaloric effect (IMCE) around 175 K indicating presence of significant AFM correlation. The MCE study reveals a clear paramagnetic (PM) to ferromagnetic (FM) transition near room temperature (T ~ 325K) which is followed by onset of AFM at lower temperatures. The development of the FM-like magnetic state at low temperature is attributed to the enhanced double exchange (DE) driven ferromagnetism in AFM state as predicted by recent theoretical studies. INTRODUCTION The physics of mixed valence perovskite manganites with a general formula R1-xBxMnO3 (R – rare earth, B- bivalent ion) has been a topical area of research over the last few decades [1]. These systems possess very rich physical properties as a result of the interplay between many complex interactions. In addition to this, manganites exhibit many intriguing phenomena such as colossal magnetoresistance (CMR), giant magnetocaloric effect (MCE) etc, which have direct relevance in different practical applications [1-2]. A current trend of research in this area is to understand the modification in the properties of these systems when they are synthesized in nanostructured forms [3-14]. In this regard, the systems were mostly studied in the forms of nanoparticles and thin films (~ nm thickness) [3-14]. However, recently there have been reports regarding successful synthesis of manganite nanowires and the investigation of their properties in comparison to their bulk counterpart [11, 15-18]. In addition to the different physical and electronic properties, the magnetocaloric properties of manganites attract considerable research interest [2]. Magnetic refrigeration based on the MCE of a magnetic material is considered as a promising alternative to conventional gas compression refrigeration technology and it is believed that manganites have most of the essential characteristics desirable in potential magnetic refrigerants. Besides the application perspective, the study of MCE in manganites is interesting from a fundamental point of view as it can provide valuable information to understand the complex magnetic properties of these systems [3, 19]. Moreover, such study is often helpful to probe different magnetic phase transitions and competing magnetic phases, which may not be easily determined by other
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conventional experiments such as dc magnetization, transport etc. [3]. Although there are a few reports highlighting in
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