Specific heat and isothermal magnetocaloric effect for single-crystal UAs
Abstract
Two complementary quantities, the specific heat at a constant magnetic field (CB) and the isothermal magnetocaloric coefficient (MT), have been investigated for a UAs single crystal in the range of T=20 160 K and B=0-13 T. Both measurements have been performed by a method using a miniature heat-flux meter as a sample support. All phase transitions between paramagnetic phase, two types of antiferromagnetic (single-k type I and double-k type IA) phases, and two types of ferrimagnetic (single-k and double-k) phases have been found to be of first order, and their entropy jumps have been estimated. It was directly shown by magnetocaloric measurements that the entropy jump at a phase transition upon increasing magnetic field may be either positive or negative, depending on the slope of the phase transition line. A three-dimensional plot of the singular part of the magnetic entropy was constructed using both CB and MT data. Peculiar features, such as a precursor anomaly occurring about ∼2 T before the paramagnetic/single-k ferrimagnetic transition (possibly related to the so-called Lifshitz instability) and a first-order transition without any latent heat occurring at the inversion point on the double-k type IA/ferri-2k phase transition line, bearing some analogy with the p-T phase diagram of 3He, are discussed.
- Publication:
-
Physical Review B
- Pub Date:
- May 2003
- DOI:
- 10.1103/PhysRevB.67.184406
- Bibcode:
- 2003PhRvB..67r4406P
- Keywords:
-
- 75.50.Ee;
- 75.50.Gg;
- 75.40.-s;
- 75.30.Sg;
- Antiferromagnetics;
- Ferrimagnetics;
- Critical-point effects specific heats short-range order;
- Magnetocaloric effect magnetic cooling