- Petr Opletal: Critical behavior in UTX compounds
- 11. 1. 2017, 14:30
- lecture room F2, first floor Ke Karlovu 5
- more information
Abstract:
Phase diagrams of antiferromagnets and connected quantum criticality are well studied part of solid state physics. In case of ferromagnets, theory predicts first-order quantum phase transition, but only for sufficiently clean systems. In weak ferromagnets second-order transition is separated from low-temperature first-order transition by tricritical point. By application of magnetic field tricritical wings appear, with their wing tips located in zero temperature. Most of experimental investigation of tricritical point and first-order transition reported in literature was done using hydrostatic pressure.
UTX family, especially ferromagnetic compounds crystallizing in hexagonal ZrNiAl structure are good candidate for investigation due to the similarities in magnetic properties and mechanisms behind. UCoAl is well known compound, 5f metamagnet exhibiting wings induced by magnetic field (TCP as described above is unreachable), yet FM state could be induced by alloying. The observation of TCP and metamagnetic wings, consequently, has been reported for URhAl under pressure (4.9 GPa [1]).
We prepared single crystals of UCo1-xRuxAl with concentration x = 0.01 and x = 0.005. Doping by ruthenium induces ferromagnetism. We present investigation of thermal expansion, magnetic and transport properties in ambient and hydrostatic pressure. Obtained data are used to construct phase diagram with focus on TCP and the first-order transition at low temperatures.
1. Yusei Shimuza, et. al., Unusual strong spin-fluctuation effects around the critical pressure of the itinerant Ising-type ferromagnet URhAl , Phys. Rev. B, 91:125115, 2015