ESR study of the spin ladder with uniform Dzyaloshinskii-Moria interaction

TL;DR

This study investigates the evolution of ESR absorption in a spin ladder magnet, revealing how uniform Dzyaloshinskii-Moriya interaction influences line broadening, excitation degeneracy lifting, and relaxation regimes across a wide temperature range.

Contribution

It demonstrates that uniform Dzyaloshinskii-Moriya interaction is the main mechanism affecting ESR in DIMPY, highlighting its role in relaxation and excitation properties in spin ladder systems.

Findings

ESR relaxation exhibits a staircase of crossovers with temperature.

Uniform Dzyaloshinskii-Moriya interaction causes ESR line broadening.

Weak splitting of ESR absorption reveals lifting of triplet degeneracy.

Abstract

Evolution of the ESR absorption in a strong-leg spin ladder magnet (C$_7$H$_{10}$N$_2$)$_2$CuBr$_4$ (abbreviated as DIMPY) is studied from 300K to 400mK. Temperature dependence of the ESR relaxation follows a staircase of crossovers between different relaxation regimes. We ague that the main mechanism of ESR line broadening in DIMPY is uniform Dzyaloshinskii-Moria interaction ($|\vec{D}|=0.20$K) with an effective longitudinal component along an exchange bond of Cu ions within the legs resulting from the low crystal symmetry of DIMPY and nontrivial orbital ordering. The same Dzyaloshinskii-Moriya interaction results in the lifting of the triplet excitation degeneracy, revealed through the weak splitting of the ESR absorption at low temperatures.