Effect of Bi doping on magnetoresistance in La 0.7-x Bi xSr 0.3MnO 3

Abstract

It is shown that upon increasing Bi content (x) in La 0.7-xBi xSr 0.3MnO 3, the ground state changes from ferromagnetic metal (x = 0) to charge ordered antiferromagnetic insulator (x > 0.4). The x = 0.3 compound shows unusual magnetic and magnetoresistive properties: it shows hysteresis in magnetization as a function of temperature, field-induced metamagnetic transition in the paramagnetic state, and nearly 100% magnetoresistance. The magnetoresistance as a function of composition at μ 0H = 5 T increases from 38% for x = 0.05 to 99.6% for x = 0.3 and then drops to 60% for x = 0.4. The unusual behavior of x = 0.3 composition is suggested to coexistence of short-range charge-ordered clusters and ferromagnetic domains. The field-induced melting of these charge-ordered clusters leads to large magnetoresista nce effect. © 2011 American Scientific Publishers.