Low-temperature magnetic phase transitions of the geometrically frustrated isosceles triangular Ising antiferromagnetCoNb2O6

Abstract

Low-temperature magnetic phase transitions of the geometrically frustrated isosceles triangular Ising antiferromagnet ${\mathrm{CoNb}}_{2}{\mathrm{O}}_{6}$ have been investigated by means of neutron diffraction down to $T=0.2\mathrm{K}$ under applied fields up to ${H}_{\ensuremath{\parallel}c}=4.4 \mathrm{kOe}.$ Below $T\ensuremath{\sim}0.6\mathrm{K},$ the relaxation time of the system becomes extremely long compared with our observation time, being responsible for all the anomalous low-temperature magnetic properties observed in the bulk measurements [T. Hanawa et al., J. Phys. Soc. Jpn. 63, 2706 (1994)]. In addition to confirmation of the triple point where the antiferromagnetic, field-induced ferrimagnetic, and incommensurate phases meet together in the ${H}_{\ensuremath{\parallel}c}--T$ magnetic phase diagram, we also found various ordered phases that are field induced between the ferrimagnetic and saturated paramagnetic phases.