Modes of magnetic resonance of S=1 dimer chain compound NTENP

TL;DR

This study investigates the spin dynamics of the S=1 dimer chain compound NTENP using ESR, revealing multiple magnetic resonance modes and supporting the fermionic model as the best description of its magnetic behavior.

Contribution

It provides detailed ESR analysis of NTENP, identifying five resonance modes and demonstrating the applicability of the fermionic model over the bosonic one for this compound.

Findings

Five ESR modes observed and identified.

Doublet structure in singlet-triplet and intra-triplet modes.

Fermionic model better describes NTENP's magnetic properties.

Abstract

The spin dynamics of a quasi one dimensional $S=1$ bond alternating spin-gap antiferromagnet Ni(C$_9$H$_{24}$N$_4$)NO$_2$(ClO$_4$) (abbreviated as NTENP) is studied by means of electron spin resonance (ESR) technique. Five modes of ESR transitions are observed and identified: transitions between singlet ground state and excited triplet states, three modes of transitions between spin sublevels of collective triplet states and antiferromagnetic resonance absorption in the field-induced antiferromagnetically ordered phase. Singlet-triplet and intra-triplet modes demonstrate a doublet structure which is due to two maxima in the density of magnon states in the low-frequency range. A joint analysis of the observed spectra and other experimental results allows to test the applicability of the fermionic and bosonic models. We conclude that the fermionic approach is more appropriate for the particular case of NTENP.