Successive Magnetic Transitions of the Kagome Staircase Compound Co_3V_2O_8 Studied in Various Magnetic Fields
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For the fictitious spin-1/2 kagome staircase system Co_3V_2O_8, magnetic field-temperature (H-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 T_<c1> 〜 11.2K, T_<c2> 〜 8.8K and T_<c3> 〜 (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 T_<c1>. The sinusoidal nature of the incommensurate modulation of the ordered moment reported in the former work has been confirmed between T_<c1> and T_<c2>, 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 T_<c2> and T_<c3>, 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 (ε) 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.
- Journal of the Physical Society of Japan
Journal of the Physical Society of Japan 76(3), "34706-1"-"34706-8", 2007-03-15
The Physical Society of Japan (JPS)