Study of the magnetic structure and the cation distributions in MnCo spinel ferrites

Single-phase powder samples of the spinel ferrites MnxCo1-xFe2O4 (0.0 <= x <= 0.3) were prepared using a conventional co-precipitation method. Comparing with the samples CrxNi1-xFe2O4 (0.0 <= x <= 0.3) reported recently by our group, we found that there are two different trends in the magnetic moments (mu(exp)) per formula of samples measured at 10 K. the value of mu(exp) increased when Mn (Mn2+ with 3d(5) electron configuration) substituted for Co (Co2+ with 3d(7) electron configuration), while mu(exp) decreased when Cr (Cr2+ with 3d(4)) substituted for Ni (Ni2+ with 3d(8)). The dependences of mu(exp) on the doping level x for the two series of samples were fitted successfully, using the quantum-mechanical potential barrier model earlier proposed by our group. In the fitting process, the magnetic moment directions of the Cr3+ Cr2+ and Mn3+ cations were assumed to be antiparallel to those of the other cations in the same sublattices due to constraints arising from Hund's rules. (C) 2015 Elsevier B.V. All rights reserved.