Successive Magnetic Transitions of the Kagome Staircase Compound Co3V2O8 Studied in Various Magnetic Fields

TL;DR

This study maps the magnetic phase diagrams of Co3V2O8 under various magnetic fields, revealing complex magnetic transitions and noncollinear structures, with no ferroelectric transitions detected.

Contribution

It provides detailed magnetic phase diagrams of Co3V2O8 in different magnetic fields, confirming noncollinear magnetic structures and the role of geometrical frustration.

Findings

Three magnetic transitions identified at zero field.

Noncollinear magnetic structures confirmed in all ordered phases.

Magnetic phases are highly sensitive to applied magnetic fields.

Abstract

For the spin-3/2 kagome staircase system Co3V2O8, magnetic field (H)-temperature (T) phase diagrams have been constructed for the fields along three principal directions up to 5 T, using results of various macroscopic measurements on single crystal samples and also using neutron diffraction data taken on both powder and single crystal samples under H along c. In zero magnetic field, the system exhibits three transitions at temperatures Tc1~11.2 K, Tc2~8.8 K and Tc3~ (6.0-7.0) K. The single crystal data present clear evidence for the noncollinear nature of the magnetic structures in all magnetically ordered phases below Tc1. The sinusoidal nature of the incommensurate modulation of the ordered moment reported in the former work has been confirmed between Tc1 and Tc2, that is, no higher harmonics of the modulation have been detected even for the present large single crystal. Even in the phase of commensurate modulation between Tc2 and Tc3, we have not detected any higher harmonics of the modulation. The phase diagrams show that the magnetically ordered phases sensitively change to other phases with H, indicating that the geometrical frustration inherent in this system is important for the determination of the phase diagram. No evidence for ferroelectric transitions has been observed in the measurements of the dielectric constant applying the electric fields along three crystallographic axes, a, b and c. Only small dielectric anomalies closely connected with the magnetic phase transitions have been found.