Magnetic properties of Bi-doped La0.5Ca0.5MnO3

Structure and magnetic properties of the La0.5−xBixCa0.5MnO3 (x=0, 1/16, 1/8, 1/4, 3/8 and 1/2) system have been experimentally investigated. The substitution of Bi3+ ion for La3+ ion systematically enhances the charge-ordering (CO) temperature. Electron spin resonance (ESR) and isothermal magnetization measurements reveal the coexistence of ferromagnetic (FM), antiferromagnetic (AFM) domains and paramagnetic (PM) matrix below TCO in 0≤x≤3/8. Kinetic hindrance to the first order charge ordering transition plays an important role in this coexisting phases. Such a coexistence of PM, FM and AFM domains leads to a compressive strain effect, resulting in a counterclockwise thermal hysteresis in M(T) curves. The hysteresis weakens with increasing Bi content, suggesting that the inner compressive strain becomes increasingly weaker. For x=1/2, only AFM state coexist with PM matrix below TCO and FM state only coexists with AFM state below ∼50 K. Therefore, almost no thermal hysteresis in M(T) curves is observed around TCO for x=1/2.