Dimensional crossover of spin chains in a transverse staggered field: an NMR study

Abstract

Heisenberg spin-1/2 chain materials are known to substantially alter their static and dynamic properties when experiencing an effective transverse staggered field originating from the varying local environment of the individual spins. We present a temperature-, angular- and field-dependent 29Si NMR study of the model compound BaCu2Si2O7. The experimental data are interpreted in terms of the divergent low-temperature transverse susceptibility, predicted by theory for spin chains in coexisting longitudinal and transverse staggered fields. Our analysis first employs a finite-temperature "Density Matrix Renormalization Group" (DMRG) study of the relevant one-dimensional Hamiltonian. Next we compare our numerical with the presently known analytical results. With an analysis based on crystal symmetries we show how the anisotropic contribution to the sample magnetization is experimentally accessible even below the ordering temperature, in spite of its competition with the collinear order parameter of the antiferromagnetic phase. The modification of static and dynamic properties of the system due to the presence of a local transverse staggered field (LTSF) acting on the one-dimensional spin array are argued to cause the unusual spin reorientation transitions observed in BaCu2Si2O7. On the basis of a Ginzburg-Landau type analysis, we discuss aspects of competing spin structures in the presence of magnetic order and the enhanced transverse susceptibility.

14 pages, 7 figures

References in corpus (3)

• NMR evidence for a strong modulation of the Bose-Einstein Condensate in BaCuSi${}_2$O${}_6$
• Electron spin resonance in the $S$=1/2 quasi-one-dimensional antiferromagnet with Dzyaloshinskii-Moriya interaction BaCu$\_2$Ge$\_2$O$\_7$
• Multiple spin-flop phase diagram of BaCu2Si2O7

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• Local spin relaxation within the random Heisenberg chain
• Impact of strong disorder on the static magnetic properties of the spin-chain compound BaCu2SiGeO7
• From order to randomness: Onset and evolution of the random-singlet state in bond-disordered BaCu${}_2$(Si${}_{1-x}$Ge${}_x$)${}_2$O${}_7$ spin-chain compounds
• Inhomogeneous ordering in weakly coupled Heisenberg $S=1/2$ chains with random bonds
• Novel magnetic field tuning of quantum spin excitations in a weakly coupled $S=$1/2 Heisenberg spin chain as seen from NMR
• Phase diagram of low-dimensional antiferromagnets with competing order parameters: A Ginzburg-Landau-theory approach
• NMR study of the spin correlations in the $S=1$ armchair chain Ni${}_2$NbBO${}_6$