Two ferromagnetic transitions in Pr0.8Ca0.2MnO3

The magnetic and structural properties of a single crystal of Pr0.8Ca0.2MnO3 have been investigated by neutron powder diffraction and bulk magnetization as a function of temperature. Two ferromagnetic (FM) transitions near 140 and 70 K, which are ascribed to the ordering of Mn and Pr spins, respectively, are clearly evidenced by both measurements. The low temperature FM transition is largely dependent upon a strong exchange coupling between the localized Pr 4f and the neighboring itinerant Mn 3d spins. Near 140 K distinctive changes occur in lattice parameters, whereas no anomalous variation develops near 70 K.