Magneto-Electric Properties in Neodymium Yttrium Manganites

Doping rare earth manganites with smaller cations results in a new family of manganites with properties comparable to rare earth manganites. Neodymium manganite was doped with yttrium to simulate the magnetoelectric properties of rare earth manganites to investigate the evolution of the multiferroic properties. Polycrystalline samples and single crystals were synthesized, magnetic properties of the samples were measured as well as the x-ray and neutron diffraction patterns to initially map out a phase separation where the A-type antiferromagnetic order co-exists with a modulated spin order. Neutron diffraction proved this transition and the temperature dependence of the modulated spin order from paramagnetic to a collinear spin density wave along the b-direction and at 2 K to form a cycloidal structure with the cycloid in the bc plane propagating along the b-direction. Physical property measurements confirmed that with the spin cycloid the material exhibits a spontaneous polarization along the c-direction that can be flopped from c to a by applying a magnetic field. The transition to the multiferroic state exhibit a complex behavior.