Effect of Sr doping on structural and magnetic behavior of SmBa1−xSrxCo2O5+δ (x = 0 and 1)

Layered double perovskite, SmBa1−xSrxCo2O5+δ (x = 0, δ = 0.5 and x = 1, δ = 1) samples were prepared by solid state reaction method. X-ray diffraction studies show that the SmBaCo2O5.5 sample crystallizes in the orthorhombic crystal structure with Pmmm space group, whereas SmSrCo2O6 sample crystallizes in the orthorhombic crystal structure with Pnma space group. The temperature dependent magnetization of the SmBaCo2O5.5 sample shows a paramagnetic (PM)-ferromagnetic (FM) and a FM-antiferromagnetic (AFM) transitions at TC = 267 K and TN = 221 K, respectively. In contrast, the SmSrCo2O6 sample shows a PM-FM transition at TC = 175 K. According to Goodenough-Kanamori-Anderson rules, the ferromagnetic behavior in SmSrCo2O6 can be understood from the super exchange interaction between the intermediate spin Co3+ and low spin Co4+ via O2- (IS Co3+ -O2- - LS Co4+). The change in magnetic entropy (∆SMmax) is found to be maximum for the SmSrCo2O6 sample.