Study of coexisting phases in Bi doped La_0.67Sr_0.33MnO₃

Nagaiah Kambhala, M. Chen, P. Li, X.-x. Zhang, D. Rajesh, K.S. Bhagyashree, L. R. Goveas, S.V. Bhat, P. Anil Kumar, R. Mathieu, S. Angappane,
J. Magn. Magn. Mater. 406, 22–29 (2016).

Temperature dependence of the resistivity and field cooling magnetization of polycrystalline Bi doped La_0.67-xSr_0.33MnO₃ (x=0, 0.1, 0.2, 0.3, 0.4 and 0.5), i.e., Bi0, Bi1, Bi2, Bi3, Bi4 and Bi5.

We study the remarkable phase separation behaviour in large bandwidth material, La_0.67Sr_0.33MnO₃ which is doped with Bi³⁺ ion at La site. The samples were prepared by standard solid state reaction route. La_0.67-xBi_xSr_0.33MnO₃ samples show the rhombohedral structure up to x=0.3, while the XRD peaks split and changes shape for x ≥ 0.4, indicating the transition to orthorhombic structure. The structural changes imply that in our Bi doped La_0.67Sr_0.33MnO₃, the increase of bond length and decrease of bond length and bond angle are elucidated. The metal-insulator transition and paramagnetic to ferromagnetic transition temperatures are found to decrease with increase of Bi doping till x = 0.3. The samples of x ≥ 0.4 show the insulating charge ordered nature. Markedly, the field dependant magnetization studies of La_0.67-xBi_xSr_0.33MnO₃ (x=0.3) show the metamagnetic nature of ferromagnetic metallic state implying the competition of coexisting ferromagnetic metallic and charge ordered antiferromagnetic insulating phases. The magnetization studies of La_0.67-xBi_xSr_0.33MnO₃ (x>0) show the stepwise behaviour which is attributed to the phase separation of ferromagnetic metallic and charge ordered antiferromagnetic insulator phases. The higher doping, La_0.67-xBi_xSr_0.33MnO₃ (x=0.4 and 0.5) samples show the dominant charge ordered antiferromagnetic phase coexisting with ferromagnetic clusters. The electron spin resonance (ESR) and exchange bias studies also substantiate the coexistence of ferromagnetic clusters in antiferromagnetic matrix. Remarkably, the ESR study along with electrical transport and magnetic studies help to ascertain the coexisting phases in the polycrystalline Bi doped La_0.67Sr_0.33MnO₃ samples.