Anomalous Behavior of Peak Resistance Temperature for Low x in As-Deposited La 1-x Ca x MnO 3 Films on NdGao 3 and SrTiO
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ANOMALOUS BEHAVIOR OF PEAK RESISTANCE TEMPERATURE FOR LOW x IN AS-DEPOSITED LatxCaxMn0 3 FILMS ON NdGaO 3 AND SrTiO3 SUBSTRATES P.R. BROUSSARD*, V.C. CESTONE** *Code 6342, Naval Research Lab, Washington, DC 20375-5343, phillip.broussard(o.,nrl.navy.mil **Code 6342, Naval Research Lab, Washington, DC 20375-5343, [email protected] ABSTRACT We have grown thin films of Lal1xCaMnO3 using off-axis cosputtering for x < 1/3 onto (001) NdGaO 3 and (100) SrTiO3 substrates from individual targets of LaMnO 3 and La 2 / 3Cal/ 3 MnO 3 . As-deposited films of La2/3Cal/ 3MnO3 on NdGaO 3 have a peak resistance temperature of 1 260 K. We see a difference in the peak temperature between the two types of substrates of z 15 K, with samples on NdGaO 3 having higher peak temperatures. As the value of x is reduced from 1/3, the peak resistance temperature decreases until x Z0.15, when the peak temperature has an upturn. Even down to x-0 we still observe a metal-insulator transition (at 185 K) for films on NdGaO 3 , while samples on SrTiO 3 show only activated behavior. We also find a scaling relationship between the peak temperature and the resistivity activation energy of the films. INTRODUCTION The characterization of thin films of La 1-CaxMnO 3 for a wide range of x has been an area of active interest recently, especially for the investigation into the nature of the high temperature transport [1]. In those studies, the films were grown on LaA10 3 and had to be annealed for long periods at high temperatures in order to obtain films with low resistivities and high transition temperatures. As an extension of work at NRL on spin polarized transport,[2] we have begun a study on the properties of as-deposited La I CaMnO3 thin films for x
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