Abstract :
Neutron diffraction and ac susceptibility measurements on La0.5−xYxCa0.5MnO3 compounds with x=0 and 0.1 have been carried out to understand the magnetic behaviour arising due to lowering of the A-site ionic radii. We find that the CE-type antiferromagnetic order observed at low temperatures for x=0 totally disappears and instead ferromagnetic order (TC∼100 K) sets in for x=0.1. The average bond distance increases while bond angle decreases on substitution of Y. The observed ferromagnetic behaviour is consistent with that predicted for a system with an average A-site cation radius 〈rA〉 of 1.183 Å based on the temperature versus 〈rA〉 phase diagram.
