Magnetic properties of RE0.7Ca0.3Mn0.95Fe0.05O3 (RE=Sm and Gd) manganites at low temperature

The magnetic properties of RE0.7Ca0.3Mn0.95Fe0.05O3 perovskite with rare-earth cations (RE=Sm and Gd) were investigated by means of X-ray diffraction, Moessbauer spectroscopy, and low temperature (4.2-266 K) magnetization measurements. Structural characterization of these compounds shows that they both have orthorhombic (Pbnm) structure. The Moessbauer spectra show clear evidence of local structural distortion of the Mn(Fe)O6 octahedron, which is based on the non-zero nuclear quadrupole interactions for high-spin Fe3+ ions. It was found that the local structural distortion increases significantly when Sm3+ is replaced by Gd3+. This distortion is attributed to the Jahn-Teller coupling strength as estimated from the Moessbauer effect results. The magnetic results indicate that the Curie temperature decreases as a result of replacing Sm by Gd. This is due to the decrease of the average A-site cationic radius . The rapid increase of magnetization at low temperature indicates the magnetic ordering of rare earth ions at the A-site.