Effect of B-site doping in (La0.3Pr0.7)0.65Ca0.35Mn1−xBxO3(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)0.65Ca0.35Mn1−xBxO3(La0.3Pr0.7)0.65Ca0.35Mn1−xBxO3 (B=Fe, Cr, Ru and Al; (0≲x≲0.100≲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 TN≈175K and TCO≈225K. 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 TC≈200K and TMI≈125K and no significant change in TC and TMI 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 TN≈160K, TC≈120K and TMI≈100K. On further increasing the Ru doping (0.03≤x≤0.05)(0.03≤x≤0.05), increase in both TC and TMI 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)(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 non-magnetic dopants Ru and Al leads to coexisting ferromagnetic and antiferromagnetic phases.

► The effect of doping at the Mn-site of AFM CO manganites has been investigated.
► Neutron diffraction study shows strong influence on the magnetic state.
► Coexisting FM and AFM phases is observed in Ru and Al doped samples.
► Fe and Cr doping leads to either a FM or an AFM ordering.