Field Induced Staggered Magnetization and Magnetic Ordering in $Cu_2 (C_5 H_{12} N_2)_2 Cl_4$

TL;DR

This study uses NMR to explore magnetic field effects in a gapped spin-1/2 compound, revealing a persistent transverse staggered magnetization influenced by Dzyaloshinskii-Moriya interactions, challenging the BEC universality class of the phase transition.

Contribution

It demonstrates the presence of a unique transverse staggered magnetization induced by magnetic fields, explained by intra-dimer Dzyaloshinskii-Moriya interactions, and predicts a non-BEC universality class transition.

Findings

Discovery of a field-induced transverse staggered magnetization

Persistence of TSM below and above the FIMO phase

Dzyaloshinskii-Moriya interactions explain TSM behavior

Abstract

We present a $^2$D NMR investigation of the gapped spin-1/2 compound $Cu_2 (C_5 H_{12} N_2)_2 Cl_4$. Our measurements reveal the presence of a magnetic field induced transverse staggered magnetization (TSM) which persists well below and above the field-induced 3D long-range magnetically ordered (FIMO) phase. The symmetry of this TSM is different from that of the TSM induced by the order parameter of the FIMO phase. Its origin, field dependence and symmetry can be explained by an intra-dimer Dzyaloshinskii-Moriya interaction, as shown by DMRG calculations on a spin-1/2 ladder. This leads us to predict that the transition into the FIMO phase is not in the BEC universality class.