AC hopping conductance in nanocomposite films with ferromagnetic alloy nanoparticles in a PbZrTiO3 matrix

In this work, the temperature and frequency dependences of the real part of the admittance of annealed nanocomposite films containing Co45Fe45Zr10-based nanoparticles covered with native oxides and embedded in a doped PbZrTiO3 ferroelectric matrix were studied. The nanocomposites studied were deposited by ion sputtering a complex target in a mixed Ar/O2 atmosphere followed by a 15-min annealing process (with steps of 25 K) in air in the temperature range of 398 K < Ta < 573 K. The conductivity of the annealed samples was measured in the temperature range of 77 K< Tp < 373 K at frequencies of 50 Hz< f< 1 MHz. The observed r(f, T) dependences confirmed that the annealed samples displayed the effects of negative capacitance over the whole frequency and temperature ranges studied because of the pronounced oxidation of the nanoparticles. The r(f, T) dependences obtained are described using an earlier-developed AC hopping conductance model. Comparisons between experimental and simulation results allow the model parameters to be estimated, such as the activation energies of the hopping conductance and the lifetimes of the electrons in the nanoparticles