Closely related magnetic and dielectric transitions in the “114” magnetoelectric Zn-doped CaBaCo₄O₇

We report on the impact of zinc doping upon the magneto-electric properties of CaBaCo₄O₇.We show that the presence of less than 1% Zn at the Co sites decreases T_C from 64 K to 48 K and generates two magnetic transitions, concomitant with changes of slope of dielectric permittivity, at 54 K and 77 K, respectively. Powder neutron diffraction and magnetic data show the existence of an incommensurate magnetic phase and a spin-flop transition in this temperature range. The crossover of the magnetodielectric effect of this oxide, from positive below 50 K to negative above this temperature emphasizes the primordial role of the incommensurate magnetic phase in the evolution of these properties