Competition of magnetic interactions in M3Fe4V6O24 (M(II) = Zn, Cu, Mn, Mg) compounds studied by EPR

Multicomponent vanadates M3Fe4V6O24 (M = Zn(II) and Mn(II)) have been synthesized using the solid-state reaction method from appropriate MO, V2O5, and Fe2O3 metal oxides. The temperature dependence of the electron paramagnetic resonance (EPR) spectra has been performed in the 90–290 K temperature range. Both the resonance field and the integrated intensity of the EPR spectrum have shown a minimum at ∼220 K. Comparison with the results of related study on the M3Fe4V6O24 (M = Mg(II) and Cu(II)) compounds has been made. The observed behaviour of the EPR integrated intensity is similar to what is registered for the nanoscale systems of the exchange coupled magnetic ions. The thermal effect of the EPR parameters is more pronounced if two different magnetic ions are present in the same sublattice. The short-range ordered spin clusters interaction and reorientation in the high temperature range could change an effective internal magnetic field which in turn modifies the resonance condition and shifts the observed resonance line. This behaviour could be attributed to the inherent magnetic inhomogeneity of the system (magnetic multiphase) due to the presence of various valence states of the magnetic ions.