Magnetic Transitions in CsNiCl3

Abstract

Recent NMR and specific-heat measurements have revealed the presence of magnetic phase transitions in CsNi${\mathrm{Cl}}_3$ at 4.85 and 4.4°K. Previous neutron-diffraction studies have revealed only one transition and we have, therefore reexamined a single crystal of CsNi${\mathrm{Cl}}_3$ in the temperature range 1.6-5.0 °K by means of this technique. The use of neutrons of wavelength of 2.46 instead of 1.03Å gives improved resolution and peak-to-background ratio, and our study confirms the presence of two magnetic phase transitions. The first of these corresponds to the onset of antiferromagnetic order and the second is interpreted as a 90° reorientation of the basal-plane component of the magnetic moment. In addition, the triangular structure observed at 1.6°K has been found to undergo considerable modification as the temperature approaches 4.4 °K.