Random Transverse Field Effects on Magnetic Noise in Spin Systems

TL;DR

This paper investigates how random transverse fields influence magnetic noise and defect dynamics in spin systems like spin ice and Ising chains, revealing new timescales and dynamical behaviors relevant to disordered magnetic materials.

Contribution

It introduces a Lindbladian framework combining simulations and exact diagonalization to analyze the effects of sparse transverse fields on magnetic dynamics in disordered spin systems.

Findings

Emergence of an additional timescale related to single-spin flip dynamics.

Sub-diffusive behavior of defects at low temperatures.

Framework applicable to experimental systems like oxygen-diluted Ho$_2$Ti$_2$O$_7$.

Abstract

Motivated by experimental developments in non-Kramers spin ice materials and the unclear role of disorder therein, we study the impact of random transverse fields on the dynamics of correlated magnetic systems. We model the effect of dilute, randomly placed transverse fields on quantities such as magnetic noise/susceptibility and the diffusivity of topological excitations. We consider a random ferromagnetic Ising chain (RTFIC) as well as three-dimensional spin ice. At low temperatures, both exhibit (sub-)diffusive defect dynamics, i.e., of domain walls and magnetic monopoles, respectively. Introducing sparse transverse fields leads to the emergence of an additional timescale on the order of the single-spin flip time. We develop a Lindbladian framework that combines Monte Carlo simulations and exact diagonalization which allows us to characterize the dynamics and develop an analytical understanding of the phenomenon. This framework can be benchmarked in detail for the RTFIC. Our findings provide insights into the magnetization dynamics of disordered non-Kramers oxides, such as oxygen-diluted Ho$_2$Ti$_2$O$_7$, and offer a framework for interpreting experimental observations in these systems.