Temperature Sensibility of Complex Permittivity in Ni–Zn Ferrite at Different Temperatures in the 700 MHz–1 GHz Range

Abstract

This paper presents a study on the behavior of complex permeability and permittivity of a Ni-Zn ferrite, at temperatures between -40 °C and 50 °C, in frequencies from 1 MHz to 3 GHz. Complex permeability and permittivity data are presented for this frequency range. We observed that the real part of permittivity (e' ) has low-temperature sensibility from 700 MHz up to 1 GHz, caused by the overlapping of two different relaxation processes, and the definition of a thermal coefficient of e' corroborated these results. Outside this frequency range, temperature variations have a greater influence in permittivity. Havriliak-Negami functions were used to describe e behavior for each measured temperature. The measurements of the real and imaginary parts of magnetic permeability μ' and μ'' showed that they decrease with frequency, which is the typical behavior for this ferrite, and that lower temperatures have higher values for both μ' and μ'' after 50 MHz.