Magnetic phase transformation in La_{0.7- x}Bi_xSr_0.3MnO₃ (0.25 ≤ x ≤ 0.40)

We have observed cross over from Ferromagnetism (FM) to Anti-ferromagnetism (AFM) accompanied by spin lattice coupling in La_{0.7- x}Bi_xSr_0.3MnO₃ as La is partially replaced by Bi (0.25 ≤ x ≤ 0.40) through structural, magnetization and electrical resistivity studies. Ferromagnetic metallic (FMM) phase observed in x = 0.25 sample transforms to antiferromagnetic insulating (AFI) phase with increasing Bi content (x = 0.40). The step like behavior in M(H), i.e. the metamagnetic transition, describes the field induced antiferromagnetic to ferromagnetic transition in x = 0.30 and 0.35 samples. The irreversibility in the field dependent resistivity and magnetization suggests the competitive phase coexistence, between AFM and FM phases, in x = 0.30 and 0.35 samples. The anomaly in the structural parameters across the electrical and magnetic transition observed from the analysis of synchrotron X-ray diffraction data, at low temperatures, establishes a strong interplay between spin lattice coupling in all four samples studied here. The present study thus clearly brings out cross over from FMM to AFI state as Bi concentration increases in La_{0.7- x}Bi_xSr_0.3MnO₃.