Critical behavior in the heat capacity of Fe[S_{2}CN(C_{2}H_{5})_{2}]_{2}Cl: Evidence for chiral universality
Abstract
The heat capacity of Fe[S_{2}CN(C_{2}H_{5})_{2}]_{2}Cl 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=(TT_{c})/T_{c} of the transition, both above and below T_{c}, leads to a value T_{c}=2.442_{4} 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 T_{c}, i.e., C(mag)~t^{α}, yields α~=0.22 for reduced temperatures above 0.01. A few data at temperatures yet closer to T_{c} 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 T_{c} given above and α=0.244+/0.005, along with other parameters. The α is more consistent with the threedimensional (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.
 Publication:

Physical Review B
 Pub Date:
 March 2002
 DOI:
 10.1103/PhysRevB.65.094403
 Bibcode:
 2002PhRvB..65i4403D
 Keywords:

 75.40.Cx;
 75.10.b;
 75.50.Dd;
 65.40.b;
 Static properties;
 General theory and models of magnetic ordering;
 Nonmetallic ferromagnetic materials;
 Thermal properties of crystalline solids