Neutron Diffraction Study of the Magnetic Properties of the Series of Perovskite-Type Compounds [(1-x)La, xCa]MnO3

A study has been made of the magnetic properties of the series of perovskite-type compounds [(1-x)La, xCa]MnO₃. The investigations have been made primarily by neutron diffraction methods, but x-ray diffraction measurements of lattice distortions and ferromagnetic saturation data are also included. This series of compounds exhibits ferromagnetic and antiferromagnetic properties which depend upon the relative trivalent and tetravalent manganese ion content. The samples are purely ferromagnetic over a relatively narrow range of composition (x~0.35) and show simultaneous occurrence of ferromagnetic and antiferromagnetic phases in the ranges (0<x<0.25) and (0.40<x<0.5). Several types of antiferromagnetic structures at x=0 and x>0.5 have also been determined. The growth and mixing of the various phases have been followed over the whole composition range, the ferromagnetic and antiferromagnetic moment contributions to the coherent reflections have been determined, and Curie and Néel temperatures have been measured. The results have been organized into a scheme of structures and structure transitions which is in remarkable accord with Goodenough's predictions based on a theory of semicovalent exchange.