Field Induced Staggered Magnetization and Magnetic Ordering in Cu$_2$(C$_5$H$_{12}$N$_2$)$_2$Cl$_4$

M. Clemancey (1) , H. Mayaffre (1) , C. Berthier (1, 2) , M. Horvatic (2) , J.-B. Fouet (3) , S. Miyahara (4) , F. Mila (5) , B. Chiari (6) , O. Piovesana (6)

1 LSP - Laboratoire de Spectrométrie Physique
2 LCMI-GHMFL - Laboratoire des champs magnétiques intenses
3 IRRMA - Institut Romand de Recherche Numerique en Physique des Materiaux
4 Department of Physics and Mathematics [Sagamihara]
5 Institute of Theoretical Physics, EPFL
6 Dipartimento di Chimica [Perugia]

We present a $^2$D NMR investigation of the gapped spin-1/2 compound Cu$_2$(C$_5$H$_{10}$N$_2$D$_2$)$_2$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.

Mots clés: Cu(Hp)Cl; Quantum Spin System; DzYaloshinskii-Moriya Interaction; Bose-Einstein Condensation; Transverse Staggerad Magnetization; NMR; DMRG

Domaines: Electrons fortement corrélés [cond-mat.str-el]

M. Clemancey, H. Mayaffre, C. Berthier, M. Horvatic, J.-B. Fouet, et al.. Field Induced Staggered Magnetization and Magnetic Ordering in Cu$_2$(C$_5$H$_{12}$N$_2$)$_2$Cl$_4$. Physical Review Letters, 2006, 97 (20 OCTOBER 2006), pp.167204. ⟨10.1103/PhysRevLett.97.167204⟩. ⟨hal-00096668⟩