Effect of heterovalent substitution at Mn site on the magnetic and transport properties of La0.67Sr0.33MnO3La0.67Sr0.33MnO3

Magnetic and transport properties of Ti substituted La0.67Sr0.33MnO3La0.67Sr0.33MnO3 are drastically affected with a change in preparation conditions. Low temperature infra-red absorption measurements reveal that this is perhaps due to inhomogeniety in substitution of Ti4+Ti4+ on Mn sites. It is found that, in the high temperature annealed samples, the substitution of Ti supresses the double exchange interaction due to the formation of Mn3+Mn3+–O–Ti4+Ti4+ chains. While in the low temperature annealed case substitution of Ti causes formation of isolated ferromagnetic clusters linked to each other by a variable range hopping polaron.