Magnetic structure of the manganites heavily doped by Fe and Cr ions

Abstract

Powder neutron diffraction and magnetic studies have been performed for NdMn 0.5Fe 0.5O 3 and NdMn 0.5Cr 0.5O 3 manganites. In NdMn 0.5Cr 0.5O 3, magnetic structure has been revealed consisting of ferromagnetic and G-type antiferromagnetic components as result of a 3d-ions magnetic moments ordering. Magnetic moments of Nd-ions are parallel to the ferromagnetic component. In NdMn 0.5Fe 0.5O 3 only the antiferromagnetic G-type structure has been found whereas Nd-sublattice was not ordered. In the both compounds, magnetic moments of 3d-ions are significantly less than one can expect, what is interpreted in terms of intrinsic chemical inhomogeneity. Magnetic phase diagrams have been constructed for the Nd(Mn 1− x M x )O 3 (M=Fe, Cr) systems, interpreted assuming superexchange interactions Mn 3+–O–Cr 3+ to be positive, Mn 3+–O–Fe 3+ negative and taking into account a disordered arrangement of Mn and Cr ions in the crystal structure sublattice as well as interplay between Jahn–Teller effect and superexchange interactions.