Effects of dilution on magnetic and transport properties of La0.7Ca0.3Mn1-xM'xO3

TL;DR

This study investigates how substituting non-magnetic elements Al and Ti into La0.7Ca0.3MnO3 affects its magnetic and transport properties, revealing weakened ferromagnetism, reduced metallicity, and increased magnetoresistance, with implications for magnetic interactions.

Contribution

It provides new insights into the effects of Mn lattice dilution on magnetic interactions and transport in La0.7Ca0.3MnO3, highlighting the role of antiferromagnetic superexchange.

Findings

Tc decreases linearly with substitution level x

Magnetoresistance is strongly enhanced by dilution

Antiferromagnetic superexchange is significant in La0.7Ca0.3MnO3

Abstract

Magnetic and transport properties of La0.7Ca0.3Mn1-xM'xO3 (M'=Al,Ti) are studied. The dilution of the Mn lattice results in a weakening of the ferromagnetism, a deterioration of the metallic conductivity, and a strong enhancement of the magnetoresistance. Although Tc linearly decreases with x in the low substitution ranges for both M' series, the scaling behavior Tc(np) previously observed for La0.7Sr0.3Mn1-xM'xO3 [Phys. Rev. B 73, 184403 (2006)] is no longer obtained. Extrapolations of the Tc(np) linear curves to Tc=0 give np values much smaller than 1. These results suggest that, according to a molecular-field approximation, antiferromagnetic superexchange between Mn ions is significant in La0.7Ca0.3MnO3, in contrast to what observed in La0.7Sr0.3MnO3. Additionally, structural data of the Al-substituted samples suggest that variations of the eg-electron bandwidth W cannot explain the decrease of Tc in magnetically diluted manganites.