Influence of the size of dopant ion on ferromagnetic behavior of Ln0.7A0.3CoO3 system [Ln = La, Nd; and A = Ca, (Ca, Sr), Sr, (Sr, Ba), Ba]

The compounds La(0.7)A(0.3)CoO(3) [A = Ca, (Ca, Sr), Sr, (Sr, Ba), Ba] and La0.5Nd0.5Sr0.234Ba0.066CoO3 have been studied by X-ray diffraction, AC and DC magnetization and DC electrical resistivity techniques. DC magnetization studies on these compounds suggest that large thermomagnetic irreversibility observed in hole-doped cobaltates arises not due to cluster glass behavior but from ferromagnetic behavior with exchange anisotropy. It is also observed that the size of the ions occupying the rare earth site has significant effect on the structural parameters, ferromagnetic transition temperature and electrical resistivity of these compounds. (C) 1999 Elsevier Science B.V. All rights reserved.