Low-Temperature Thermal Conductivity And Magnetic Transitions Of The Kagome-Staircase Compound Ni3v2o8

The kagome-staircase compound Ni3V2O8 is an attractive multiferroic material exhibiting rich phase diagrams. However, the magnetic properties and magnetic transitions have been studied only above 1.3 K. In this work, we study the thermal conductivity kappa of Ni3V2O8 single crystals at low temperatures down to 0.3 K and in magnetic fields up to 14 T. In zero field, the magnetic transitions from the low-temperature incommensurate (LTI) phase to the commensurate phase (C) and then to a second commensurate phase (C' yield anomalies in kappa(T) curves at T-LC = 3.7 K and T-CC' = 2.0 K, respectively, which indicates a significant phonon scattering by the critical spin fluctuations. When the field is applied along the a axis, the field dependence of kappa displays four anomalies associated with different magnetic transitions and reveals an undetected magnetic state at subkelvin temperatures. In addition, the kappa(B) curves are found to depend not only on the history but also on the magnitude of the applied field. When the field is applied along the b axis, a high-field phase located above the LTI and high-temperature incommensurate phases is revealed.