Influence of Sn/Nb on the resistivity of Mn-Zn ferrites

Effect of Sn4+/Nb5+ on de resistivity as a function of dopant concentration , temperature and duration of applied field for Mn-Zn ferrites has been stu died. Frequency response of ac resistivity for all the specimens has also b een evaluated. Results are discussed considering vacancies, influence of va cancies, valence fluctuations along with hopping mechanism. Two transition temperatures Ts and Te are observed relating to change in the conduction me chanism at low temperature range and in high temperature range due to trans formation from ferromagnetic to paramagnetic state. Activation energies obt ained in low temperature range are lower than high temperature range activa tion energy values and are explained. The decrease of ac resistivity with f requency is attributed to the dielectric relaxation caused by bound charge carriers.