# Phase Diagram and Soliton Picture of an Ideal Spin-Peierls Compound D-F$_{5}$PNN

## TL;DR

This study explores the magnetic phases and excitations in the ideal spin-Peierls compound D-F$_{5}$PNN, revealing distinct phases, hysteresis, and the roles of magnons and solitons in its magnetic behavior.

## Contribution

It provides the first detailed experimental phase diagram and interprets magnetic excitations in D-F$_{5}$PNN using combined susceptibility and ESR data.

## Key findings

- Identified uniform, dimerized, and incommensurate phases with hysteresis.
- Magnon and soliton excitations explain magnetic susceptibility and ESR spectra.
- D-F$_{5}$PNN is confirmed as an ideal model for spin-Peierls transition studies.

## Abstract

We investigate magnetic properties of an $S$=1/2 quasi-one dimensional organic antiferromagnet, D-F$_{5}$PNN using magnetization measurements taken at temperatures as low as 0.5 K. Three distinct phases were observed consisting of uniform, dimerized (D), and incommensurate (I) spin structures in the magnetic field versus temperature plane, where a significant hysteresis appears between D-I transitions in the field scan measurements. A combination of magnon ($S$=1) and soliton ($S$=1/2) excitations have successfully reproduced the observed magnetic susceptibility. In addition, such excitations provide a reasonable interpretation of the temperature dependent electron spin resonance (ESR) spectra. By comparison with the theoretical study, we conclude that D-F$_{5}$PNN is an ideal compound for investigating the spin-Peierls transition.