Magnetic phase diagram of the quantum spin chain compound SrCo2V2O8: a single-crystal neutron diffraction study

L Shen,E Blackburn,J O Birk,O Zaharko,E Jellyman,Z He

doi:10.1088/1367-2630/ab2b7a

Abstract

We explore magnetic order in the quantum spin chain compound SrCo2V2O8 up to 14.9 T and down to 50 mK, using single-crystal neutron diffraction. Upon cooling in zero-field, commensurate antiferromagnetic (C-AFM) order with modulation vector = (0, 0, 1) develops below TN ≃ 5.0 K. Applying an external magnetic field (H∥c axis) destabilizes this C-AFM order, leading to an order-disorder transition between TN and ∼1.5 K. Below 1.5 K, a commensurate to incommensurate (IC-AFM) transition occurs at 3.9 T, above which the magnetic reflections can be indexed by = (0, 0, 1 ± δl). The incommensurability δl scales monotonically with H until the IC-AFM order disappears around 7.0 T. Magnetic reflections modulated by emerge again at higher fields. While the characters of the C-AFM, IC-AFM and the emergent AFM order in SrCo2V2O8 appear to fit the descriptions of the Néel, longitudinal spin density wave and transverse AFM order observed in the related compound BaCo2V2O8, our results also reveal several unique signatures that are not present in the latter, highlighting the inadequacy of mean-field theory in addressing the complex magnetic order in systems of this class.

Highlights

Magnetic field is a very important parameter when tuning the physical properties in quasi one-dimensional (1D) spin-1/2 magnets
1.5 K, a commensurate to incommensurate (IC-AFM) transition occurs at 3.9 T, above which the magnetic reflections can be indexed by kIC = (0, 0, 1 ± δl)
While the characters of the commensurate antiferromagnetic (C-AFM), IC-AFM and the emergent AFM order in SrCo2V2O8 appear to fit the descriptions of the Néel, longitudinal spin density wave and transverse AFM order observed in the related compound BaCo2V2O8, our results reveal several unique signatures that are not present in the latter, highlighting the inadequacy of mean-field theory in addressing the complex magnetic order in systems of this class

Summary

Introduction

Magnetic field is a very important parameter when tuning the physical properties in quasi one-dimensional (1D) spin-1/2 magnets. In weakly coupled spin chains or ladders with a singlet-dimer ground state (S = 0), applying a magnetic field splits the associated triplet excitation (S = 0, ±1); a singlet-dimer to LRO transition occurs at the closure of the energy gap corresponding to the lowest triplet branch (S = 1). This transition, known as magnon Bose– Einstein condensation (BEC), has been intensively studied in the last two decades [8,9,10]

Methods

Discussion

Conclusion