%0 Journal Article
%T Influence of Nd Substitution by La in on Structural and Transport Properties for Sensing Applications
%A Sudarshan Vadnala
%A Saket Asthana
%A Prem Pal
%A S. Srinath
%J ISRN Materials Science
%D 2013
%R 10.1155/2013/728195
%X The structural and transport properties of manganites with and 0.2 prepared by solid state reaction route are studied. These compounds are found to be crystallized in orthorhombic structural form. A shift in the metal-semiconductor/insulator transition temperature ( ) towards room temperature (289£¿K) with the substitution of Nd by La, as the value of is varied in the sequence (0, 0.1, and 0.2), has been provided. The shift in the , from 239£¿K (for ) to near the room temperature 289£¿K (for ), is attributed to the fact that the average radius of site-A increases with the percentage of La. The maximum temperature coefficients of resistance (TCR) of ( and 0.2) are found to be higher compared to its parent compound which is almost independent of . The electrical resistivity of the experimental results is explored by various theoretical models below and above . An appropriate enlightenment for the observed behavior is discussed in detail. 1. Introduction In the past few decades, AMnO3-type manganites have been extensively studied because of their richness in physical properties which is due to the simultaneous presence of spin, lattice, and orbital degrees of freedom [1¨C3]. Significant attention has been paid by many researchers in order to explore their potential for spacious technological applications such as read heads, magnetic information storage, low- and high-field magnetic sensors, IR detectors, and numerous other spintronic applications [4¨C11]. The substituted manganites provide high temperature coefficient of resistance (TCR) in bulk as well as in thin films at room temperature. This will motivate us to explore them for infrared radiation detectors (i.e., IR detector) for night vision applications [12]. Among all perovskite manganites, NdMnO3 is an antiferromagnetic insulator, characterized by a superexchange coupling between Mn3+ sites. This coupling is facilitated by a single electron predominated by strong correlation effects. On the other hand, partial substitution of Nd3+ ions with divalent cations (Sr, Ca, and Ba) results in mixed valance states of Mn, that is, Mn3+/Mn4+ which is responsible for the ferromagnetic Zener double exchange mechanism [13]. The most prevalent experimental way of affecting the physical properties of the manganites is either substituting cations at the A- or B-sites or varying the oxygen content in the regular perovskite structure [20¨C22]. The size mismatch at A-site generates internal chemical pressure within the lattice. Due to this structural disorder effect, the local oxygen displacement occurs, ensuing into bond
%U http://www.hindawi.com/journals/isrn.materials.science/2013/728195/