Magnetotransport properties of (La1-yPry)0.65Ca0.35MnO3 (y=0.0-0.7) showing crossover from A-type to CE-type antiferromagnetic state -: art. no. 184413

Resistivity and thermoelectric power (TEP) of (La1-yPry)(0.65)Ca0.35MnO3 [y=0.0-0.7], both in the presence and in the absence of magnetic field, have been reported. With the increase of Pr content metal-insulator transition (MIT) temperature T-p decreases while magnetoresistance increases. A little above T-p, thermoelectric power shows a peak at a temperature T-max (say) indicating existence of the A-type AFM phase for the samples with smaller y<0.7. Again with higher Pr content (y>0.2), an additional peak is observed at T-max(*) (T-max(*)<T-p<T-max). This additional peak is a resultant effect of the increase of orbital degrees of freedom (arising from collective Jahn-Teller distortion at higher Pr-concentration) and the decrease of entropy of the charge carriers (arising due to the spin polarization in the FM phase). The present system shows a changeover from the A-type AFM state to the CE-type AFM state at a "critical" concentration between y=0.6 and 0.7. The magneto-thermopower data establish well the orbital ordering in the (La1-yPry)(0.65)Ca0.35MnO3 type CMR system.