Temperature dependent neutron diffraction studies on Tb+3 doped half doped (La0.375Tb0.125)(Ca/Sr)0.5MnO3 manganites

Various interesting phenomena such as charge ordering (CO), orbital ordering (OO) and spin ordering (SO) observed in half doped manganites are of scientific interest because of their sensitivity to the variations in A-site cationic size mismatch. Temperature dependent neutron diffraction (ND) studies on CO Tb-Sr doped (LaTb)0.45(CaSr)0.55MnO3 manganite has been reported. In this communication, we report the results of the investigations on the structural, transport and magnetic properties of Tb3+ doped (La0.375Tb0.125)(Ca/Sr)0.5MnO3 (LTC/LTS) CO half doped manganite systems, using temperature dependent ND studies. Rietveld refinement of X-Ray Diffraction data reveal that the single phasic LTC and LTS samples crystallize in orthorhombic structure with Pnma and Fmmm space group, respectively. The refinement of ND data, collected at various temperatures in the range 300-22K, reveals that LTC does not show any structural transition as well as magnetic ordering up to 22K while in LTS, an emergence of a low angle (0 0 1) and (0 -1 2) peaks have been observed at 2θ ∼ 9.3° and 20.6°, respectively, below 175K with their intensity increasing with decrease in temperature. Magnetic phase refinement of the ND data clearly depicts the presence of A-type AFM phase up to 22K. Moreover, at 22K, the obtained value of magnetic moment of Mn+3 ions in a-b plane is ∼ 4.105 μβ/Mn. The results of detailed structural analysis of the temperature dependent ND measurements have been discussed in the light of size variance effects in manganites. (author)