Thermal expansion in (La0.62Pb0.38)MnO3: Possible evidence for a coupling between elastic and magnetic exchange forces

Abstract

Using single-crystal, automated diffractometer techniques, the linear coefficient of thermal expansion has been determined for La0.62Pb0.38MnO3 from 298 to 627 K. The linear coefficient of thermal expansion is observed to undergo a change from 7.2 x 10-5 A/K for T Tc to 10.8 x 10-5 A/K for T> Tc. It is concluded that while the rhombohedral distortion in the (La, Pb)MnO3 system can be understood qualitatively on the basis of ionic size and polarizability considerations alone, the quantitative systematics of the distortion parameters and the change in the linear thermal expansion coefficient at Tc indicate a significant coupling between the elastic and magnetic exchange forces.