Part 1 : Nanoparticles Module 3 : Dielectric properties of materials
Lecture 7 : Non-Debye relaxation models
 
This is known as Havriliak-Negami formula where $\mu$ and $\nu$ are empirical parameters, depending upon the nature of the experimentally observed response; usually one finds $0<\mu\le 1$ and $\mu \nu \le 1$. When $\mu=1=\nu$, one gets the classical Debye relaxation. When $\mu =1$ and $\nu\ne 1$, then the formula is known as Davidson-Cole formula. When $\mu \ne 1$ and $\nu=1$, then the formula is known as Cole-Cole formula.
A further empirical generalization of above is
MATH
where the sum over j represents different dielectric relaxation processes presumably arising from different components in the material.