Why the dipolar response in dielectrics and spin-glasses is unavoidably universal.

Eduardo Cuervo-Reyes

doi:10.1038/srep29021

Abstract

Materials response to electric or magnetic fields is often dominated by the dynamics of dipoles in the system. This is for instance the case of polar dielectrics and many transition metal compounds. An essential and not yet well understood fact is that, despite their structural diversity, dielectric solids exhibit a striking universality of frequency and time responses, sharing many aspects with the behaviour of spin-glasses. In this article I propose a stochastic approach to dipole dynamics within which the “universal frequency response” derives naturally with Debye’s relaxation mechanism as a special case. This formulation reveals constraints to the form of the relaxation functions, which are essential for a consistent representation of the dynamical slowing-down at the spin-glass transition. Relaxation functions with algebraic-, and exponential-tails, as well as damped oscillations, are shown to have a unified representation in which the stable limit of the distribution of waiting-times between dipole flips determines the present type of dynamics.

Highlights

Materials response to electric or magnetic fields is often dominated by the dynamics of dipoles in the system
A prominent example is the slowing-down of the spin dynamics associated with the on-set of a glassy phase
The algebraic tail with 0

Summary

Introduction

Materials response to electric or magnetic fields is often dominated by the dynamics of dipoles in the system. It is neither clear why power-law relaxations are so ubiquitous in nature, nor is there consensus on the description of its transformation across Tf. In this report I propose a stochastic approach to the macroscopic response, which represents the dynamics in both (ergodic and glassy) phases correctly and explains why the response in Ising-like dielectrics and spin-glasses is unavoidably universal.

Results

Conclusion