La1-xBaxMnO3의 자기-구조 전이에 대한 무질서의 역할

초록

Magnetic-field-induced structural transition has been systematically investigated for La1-xBaxMnO3 with a fine control of carrier doping, i.e., 0.15 ≤ x ≤ 0.2 The application of a magnetic field results in the suppression of rhombohedral-orthorhombic transition temperature (TS) and the increase of metal-insulator transition temperature (TMI), which indicates the stabilization of rhombohedral phase with an increase of the kinetic energy of eg electrons. Near x=0.17, we found that TS smoothly decreased with the magnetic field even though it crossed the magnetic phase boundary or metal-insulator transition boundary. Also the magnetostructural phase diagram obtained from the temperature sweep in the fixed magnetic field and from the magnetic field sweep in the fixed temperature is not so different. By comparing La1-xSrxMnO3 (x=0.17), we have suggested that the disorder originated from ionic size differences between La and Ba may weaken the sensitivity of the kinetic energy of eg carriers on the degree of lattice distortion in La1-xBaxMnO3.