The heat capacity of Fe[S2CN(C2H5)2]2Cl has been measured in the region of the 2.5 K ferromagnetic transition with much better temperature resolution than in any previous set of data on this material. Analysis of data within 0.1 in reduced temperature t=(T-Tc)/Tc of the transition, both above and below Tc, leads to a value Tc=2.4424 K. This agrees well enough with the previously established value 2.457 K, considering likely uncertainties in absolute temperature among different instruments. Simple power law analysis of the magnetic heat capacity above Tc, i.e., C(mag)~t-α, yields α~=0.22 for reduced temperatures above 0.01. A few data at temperatures yet closer to Tc suggest a larger value for α, and possible crossover; but the probability is substantial that these are transition rounding effects. A global analysis of data above and below the transition, and allowing for additional regular terms in the heat capacity, leads to the Tc given above and α=0.244+/-0.005, along with other parameters. The α is more consistent with the three-dimensional (3D) chiral Heisenberg model value 0.24+/-0.08 than with the 3D chiral XY model value 0.34+/-0.06. The leading amplitude ratio is A+/A-=0.325+/-0.005, also consistent only with chiral model results.
Physical Review B
- Pub Date:
- March 2002
- Static properties;
- General theory and models of magnetic ordering;
- Nonmetallic ferromagnetic materials;
- Thermal properties of crystalline solids