Effect of B-site doping in (La0.3Pr0.7)0.65Ca0.35Mn1-xBxO3 (B=Fe, Cr, Ru and Al) manganites

We have investigated the influence of B-site doping on the crystal and magnetic structure in (La0.3Pr0.7)(0.65)Ca0.35Mn1-xBxO3 (B=Fe, Cr, Ru and Al; (0 <= x <= 0.10)) compounds using neutron diffraction, AC and DC magnetization, specific heat and resistivity techniques. All the compounds are isostructural and crystallize in an orthorhombic structure in Pnma space group. The undoped sample (x=0) exhibits charge and orbitally ordered pseudo CE-type antiferromagnetic state with T-N approximate to 175 K and T-CO approximate to 225 K. Low concentration of dopant with and without 3d electrons exhibit differing influence on the magnetic ground state of this compound. On doping with Fe, the suppression of charge and orbitally ordered pseudo CE-type antiferromagnetic state is followed by an evolution of magnetically disordered spin glass state. Doping with Cr results in suppression of the CE-type antiferromagnetic state and emergence of localized ferromagnetic state in the intermediate compositions. In 3% Cr doped sample, the ferromagnetic metallic state is favored with T-C approximate to 200 K and T-MI approximate to 125 K and no significant change in T-C and T-MI as a function of Cr doping is found. A progressive reduction in the moment with increasing concentration of Cr indicates the suppression of ferromagnetic metallic phase, which then coexists with a spin glass state at 10% Cr doping. In the case of doping with Ru a phase separated state with coexisting ferromagnetic and antiferromagnetic phase is observed. In 1% Ru doped sample, the ferromagnetic state coexists with an antiferromagnet state, with T-N approximate to 160 K, T-C approximate to 120 K and T-MI approximate to 100 K. On further increasing the Ru doping (0.03 <= x <= 0.05), increase in both T-C and T-MI at the expense of antiferromagnetic state suggests the stabilization of ferromagnetic ordering. Similarly, with non-magnetic Al doping of 3%, the pseudo CE-type antiferromagnetic state coexists with the ferromagnetic metallic phase. With further increase in Al doping (0.05 <= x <= 0.07), both pseudo CE-type antiferromagnetic and ferromagnetic phases are gradually suppressed. This study shows that magnetic dopants Fe and Cr results in either ferromagnetic or antiferromagnetic phases whereas nonmagnetic dopants Ru and Al leads to coexisting ferromagnetic and antiferromagnetic phases. 0 2013 Elsevier By. All rights reserved.