Synthesis and characterization of Sm-based orthoferrite compounds, SmFe1-xMnxO3

Abstract

The orthoferrites RFeO3 where R is a rare earth and related compounds are being studied because of their important technological applications and unusual magnetic and electrical properties. Some of these compounds are of interest because of their ferroelectric behaviour as well as for their semiconducting properties. Several elements can be partly or completely substituted for the iron thus providing a means of preparing materials with tailor made properties. These orthoferrites can be antiferromagnetic insulators. The magnetic interactions in such cases are formed as a result of strong negative indirect Fe3+-O-Fe3+ interaction. Although these materials are very weak ferromagnetic, they exhibit many properties of ferromagnets. Since the magnetic properties are crucially dependent on both the shape, size of particles and the relative population of the sites or the cation distribution, choosing the right method of preparation becomes crucial. They have wide range of applications in magnetic recording, catalysis, pigments in paints and ceramic among others. From the previous experiments, there is fairly convincing evidence of SmFeO3 orthoferrite synthesis, albeit with some (5 – 10%) unreacted Fe2O3. Unreacted Fe2O3 is perhaps an indication of a poorly homogenized sample, and there should be better grinding-mixing procedures. The substitution of Mn ions in SmFeO3 not only weakens the exchange interaction and reduces the Curie temperature, but also induces a J-T distortion which results in a large electric field gradient at the 57Fe nucleus. During this process the crystallographic structure of the sample is modified by the substitution of Mn ions.