# Distribution of eigenstate populations and dissipative beating dynamics in uniaxial single-spin magnets

## TL;DR

This paper investigates how eigenstate populations evolve during magnetization reversal in a quantum uniaxial magnet, revealing that the delay in reversal is independent of spin size and analyzing dissipative effects on spin oscillations.

## Contribution

It extends previous simulations by analyzing eigenstate population distributions and their scattering in avoided level crossings, including dissipative effects via a Lindblad master equation.

## Key findings

- Peak distribution position is independent of spin size S.
- Delay in magnetization reversal is consistent across quantum and classical regimes.
- Dissipative effects induce damping in spin beating oscillations.

## Abstract

Numerical simulations of magnetization reversal of a quantum uniaxial magnet under a swept magnetic field [Hatomura, \textit{et al}., \textit{Quantum Stoner-Wohlfarth Model}, Phys. Rev. Lett. \textbf{116}, 037203 (2016)] are extended. In particular, how the "wave packet" describing the time-evolution of the system is scattered in the successive avoided level crossings is investigated from the viewpoint of the distribution of the eigenstate populations. It is found that the peak of the distribution as a function of the magnetic field does not depend on spin-size $S$, which indicates that the delay of magnetization reversal due to the finite sweeping rate is the same in both the quantum and classical cases. The peculiar synchronized oscillations of all the spin components result in the beating of the spin-length. Here, dissipative effects on this beating are studied by making use of the generalized Lindblad-type master equation. The corresponding experimental situations are also discussed in order to find conditions for experimental observations.