Spin-dynamics of the low-dimensional magnet (CH3)2NH2CuCl3

TL;DR

This study investigates the spin dynamics of the low-dimensional quantum magnet (CH3)2NH2CuCl3 using inelastic neutron scattering, revealing quasi-one-dimensional coupling and unexpected excitation propagation directions.

Contribution

It provides new experimental insights into the spin excitations and coupling in DMACuCl3, challenging previous models of independent dimer pairs.

Findings

Observed a 0.95 meV energy gap in excitations.

Detected a bandwidth of 0.82 meV for spin excitations.

Revealed significant quasi-one-dimensional coupling with unexpected propagation directions.

Abstract

Dimethylammonium copper (II) chloride (also known as DMACuCl3 or MCCL) is a low dimensional S=1/2 quantum spin system proposed to be an alternating ferro-antiferromagnetic chain with similar magnitude ferromagnetic (FM) and antiferromagnetic (AFM) exchange interactions. Subsequently, it was shown that the existing bulk measurements could be adequately modeled by considering DMACuCl3 as independent AFM and FM dimer spin pairs. We present here new inelastic neutron scattering measurements of the spin-excitations in single crystals of DMACuCl3. These results show significant quasi-one-dimensional coupling, however the magnetic excitations do not propagate along the expected direction. We observe a band of excitations with a gap of 0.95 meV and a bandwidth of 0.82 meV.