Phase transition between hidden and antiferromagnetic order in URu2Si2.
We have carried out thermal expansion measurements on the heavy fermion compound URu2Si2. We have discovered a new anomaly that appears only under pressure for both the tetragonal a and c axes. Plotting these temperatures on a temperature-pressure plane, we have constructed a phase diagram, in which there is a first order phase transition boundary separating a hidden and antiferromagnetic order. When the system enters the antiferromagnetic phase from the hidden order, the lattice constant shrinks along the a axis and elongates along the c axis, leading to an increase in the lattice constant ratio of c/a. We conclude that the system lies close to a bicritical point from which the first order phase transition line emanates.
Motoyama
Gaku
G
Department of Physics, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan.
Nishioka
Takashi
T
Sato
Noriaki K
NK