Effect of yttrium substitution in charge ordered antiferromagnetic La0.5Ca0.5MnO3

Neutron diffraction and ac susceptibility measurements on La0.5-xYxCa0.5MnO 3 compounds with x = 0 and 0.1 have been carried out to understand the magn etic behaviour arising due to lowering of the A-site ionic radii. We find t hat the CE-type antiferromagnetic order observed at low temperatures for x = 0 totally disappears and instead ferromagnetic order (T-C similar to 100 K) sets in for x = 0.1. The average bond distance increases while bond angl e decreases on substitution of Y. The observed ferromagnetic behaviour is c onsistent with that predicted for a system with an average A-site cation ra dius [r(A)] of 1.183 Angstrom based on the temperature versus [r(A)] phase diagram. (C) 2001 Elsevier Science Ltd. All rights reserved.