Impact of the Sr doping on structural and magnetic properties of nanocrystalline Ba1-xSrxCo0.9Mn0.1O3-δ (0 ≤ x ≤ 0.5)

We have investigated the impact of Sr-doping on physical properties of the nanocrystalline Ba_1-xSr_xCo_0.9Mn_0.1O_3-δ (0 ≤ x ≤ 0.5) samples synthesized by using sol–gel method under different annealing temperature. The X-ray diffraction patterns of the nanocrystalline samples annealed at 900 °C show 2H-type hexagonal stacking sequence which consist of one-dimensional chain of face sharing octahedra. With increase in annealing temperature, samples crystallize in mixed 2H + 12H-hexagonal polytypes, exhibiting additional terminal sharing tetrahedra. The magneto-structural properties influenced by annealing temperature under different Sr-doping level have been elaborated using spin model projection and superparamagnetic cluster contribution. The inclusion of 12H-phase showed higher magnetic moment contribution compared with single 2H-phase. The studied nanocrystalline samples show semiconducting-like electrical transport properties. The phase dependent electrical transport properties of the nanocrystalline samples have been studied using variable range hopping and small polaron hopping conduction mechanism. The synthesized samples exhibit moderate negative magnetoresistance for a field change of 5 T in the vicinity of the magnetic ordering. The numerical value of magnetoresistance suppresses with increase in Sr-doping and it shows the 2H-type hexagonal phase dominance. The relation between magnetization and electrical resistivity around the magnetic ordering temperature is well explained using magnetoresistance data and magnetization isotherms.