Effect of Y-doping on the magnetic and charge orderings in Nd2/3Ca1/3MnO3

The shifts of the magnetic and charge ordering transition temperatures caused by Nd substitution for Y in Nd2/3Ca1/3MnO3 CMR narrow-band perovskite manganite have been studied. At low temperatures, three different long-range magnetic orderings consistent with a phase separation scenario have been observed in the doped compound (Nd0.9Y0.1)(2/3)Ca1/3MnO3 by neutron-diffraction study: the anti-ferromagnetic orderings of PCE and DE types existing below similar to 110 and similar to 60K, respectively, and the ferromagnetic one of B type existing below similar to 42. Magnetic phase transformations temperatures as well as those of charge ordering have been found to be structural-dependent. Y-doping leads to the decrease of the anisotropy of the orthorhombic Pnma crystal lattice b/root 2c, which causes a decrease of the indirect exchange parameters in the system and thus a decrease in the magnetic transformation temperatures for 20-30 K in the doped compound. Doping leads as well to the higher level of the coherent Jahn-Teller distortions of the MnO6 octahedra in the 200-300 K temperature region, which results in the increase of the charge ordering temperature for similar to 80K. (C) 2008 Elsevier B. V. All rights reserved.