Relation between magnetic entropy and resistivity in La/sub 0.67/Ca/sub 0.33/MnO/sub 3/

Abstract

We present an investigation of the magnetic entropy /spl Delta/S and resistivity /spl rho/, and the relation between them, for La/sub 0.67/Ca/sub 0.33/MnO/sub 3/ film. We found that the maximum /spl Delta/S is approximately 6 J/kg/spl middot/K, and the maximum magnetoresistance (defined as /spl rho/(0)//spl rho/(H)-1) is about 400% under a field /spl mu//sub o/H of 5 T. A careful analysis gives an equation of the form /spl Delta/S=-/spl alpha//spl int//sub 0//sup H/[/spl part/ln(/spl rho/)//spl part/T]/sub H/dH (/spl alpha/=21.74 emu/g), which relates magnetic order to transport behavior of the compounds. This result reveals the predominant role of magnetic polarons on the magnetoresistive property of manganites. It also provides an alternative method to determine magnetic entropy change on the basis of resistive measurements.