Specific Heats of Triangular Spin Tube in Magnetic Fields

In this study, the temperature ( T) dependence of specific heat ( C p ) is investigated in an equilateral triangular spin tube CsCrF 4 above T = 0 . 38K under several magnetic fields ( B ). At B = 0 T, no λ -type anomaly of the temperature dependence [ C p ( T) ] appears over the entire temperature range. However, the DC and AC magnetic susceptibilities exhibit a small anomaly, which is interpreted as an antiferromagnetic phase transition at T N ∼4.5K. This difference may indicate that the large magnetic entropy at B = 0 T is spent far below T N , because a large fluctuated spin state due to geometrical spin frustration may have occurred at T = 0K. Under different magnetic fields, the C p ( T)/T curves present shoulders and/or broad peaks above B = 1 T. The electronic specific heat coefficient decreases with increasing B indicating that the magnetic ground state consists of an antiferromagnetic ordered state with large spin fluctuations, rather than a gapless spin-liquid state, and their fluctuations are sensitively suppressed by the magnetic fields.