Modulation of the ferromagnetic insulating phase in Pr0.8Ca0.2MnO3 by Co substitution

Ferromagnetic insulator Pr0.8Ca0.2Mn1-yCoyO3 (0 <= y <= 0.7) thin films were epitaxially grown by pulsed laser deposition on substrates of (LaAlO3)O-3(SrAl0.5Ta0.5O3)(0.7) (100). To probe the ferromagnetic insulator state, the Co content dependences of the structural, magnetic, and transport properties were studied. Variation of lattice constant by the Co substitution is well reproduced considering that divalent and trivalent Co ions substitute for Mn ions at the perovskite B-sites. For 0 <= y <= 0.3, the Curie temperature, saturation magnetization, and magnetoresistance increase with increasing Co content, retaining the insulating properties. Detailed analyses of transport and magnetic properties indicate the contribution of both double exchange and superexchange interactions to the appearance of the ferromagnetic insulating phase. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim