Low temperature Synthesis, and magnetic and magnetotransport properties of a (La1-xLux)(0.67)Ca0.33MnO3 (0 <= x <= 0.12) system

摘要

We have been able to synthesize Lu3+ substituted La0.67Ca0.33MnO3 (LCMO) by an auto-combustion method. Synthesis of this compound is not successful by conventional ceramic or other chemical methods. The magnetic and electrical transport properties of the Lu substituted LCMO [(La1-xLux)(0.67)Ca0.33MnO3 (0 less than or equal to x less than or equal to 0. 12)] system have been investigated and compared with those of the Y3+, Pr3+, Dy3+ and Tb3+ substituted LCMO systems. All the compounds show a ferromagnetic metal to paramagnetic insulator transition at T-C. The tolerance factor reduces from 0.917 for x = 0 to 0.909 for x = 0. 12, and for this range all are ferromagnetic metals, indicating the dominance of the coupling between spins due to double exchange over the antiferromagnetic superexchange interaction. The transition temperatures and magnetization decrease as the Lu concentration increases. This is satisfactorily accounted for on the basis of a transition from ferromagnetic at x = 0 to canted spin order for x > 0. All the samples show a higher magnitude of MR compared to that in pure LCMO at 80 kOe field in the temperature range 5-320 K. A fairly high value of low field magnetoresistance (LFMR) of about 30% is obtained in all the samples, at a field less than 5 kOe.