Abstract
We have investigated the influence of B-site doping on the crystal and magnetic structure inLa0.5Ca0.5Mn1 − xBxO3 (B = Fe, Ru, Al and Ga) compounds using neutron diffraction, small angle neutronscattering, magnetization and resistivity techniques. The B-site dopedsamples are isostructural and possess an orthorhombic structure in thePnma space group at 300 K. A structural transition from orthorhombic to monoclinic is found toprecede the magnetic transition to the CE-type antiferromagnetic state in a few of thesesamples. On doping with Fe, the charge and orbitally ordered CE-type antiferromagneticstate is suppressed, followed by growth of the ferromagnetic insulating phase in0.02 ≤ x ≤ 0.06 compounds. Athigher Fe doping in x > 0.06, the ferromagnetic state is also suppressed and no evidence oflong range magnetic ordering is observed. In Ru doped samples(0.01 ≤ x ≤ 0.05), the ferromagnetic metallic state is favored atTC≈200 K andTMI≈125 K and no significantchange in TC and TMI as a function of Ru doping is found. In contrast, with non-magnetic Al substitution for0.01 ≤ x ≤ 0.03, the charge ordered CE-type antiferromagnetic state coexists withthe ferromagnetic metallic phase. With further increase in Al doping(0.05 ≤ x ≤ 0.07), both CE-type antiferromagnetic and ferromagnetic phases are graduallysuppressed. This behavior is accompanied by the evolution of an A-typeantiferromagnetic insulating state. Eventually, at higher Al doping(0.10 ≤ x ≤ 0.13), this phase is also suppressed and the signature of a spin glass like transition is evident inM(T). Likewise, substitution with Ga is observed to induce similar effects to those described forAl doped samples. The presence of short ranged ferromagnetic ordering has been furtherexplored using small angle neutron scattering measurements in a few of the selectedsamples.
Published Version
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