- Petr Opletal: Preparation and characterization of UCoGa in the context of quantum phase transitions
- 3. 5. 2017, 14:30
- lecture room F2, first floor Ke Karlovu 5
- more information
Abstract:
Phase diagrams and quantum criticality of weak itinerant ferromagnets are in focus due to the recent development in theory and new experimental results. Four general types of phase diagram were predicted [1]. Type of phase diagram depends on compound, but also on quality of sample. We focus on phase diagram with discontinuous phase transition. Systems exhibiting discontinuous transition are characterized by tricritical point (TCP), where second order phase transition changes into first order one and is rapidly suppressed. Also at TCP first order metamagnetic transition appears. Increasing tuning parameter suppresses first order metamagnetic transition until quantum critical endpoint is reached. Few compounds exhibit whole or part of phase diagram with discontinuous transition (ZrZn2 [2], UGe2 [3], URhAl [4], UCoAl [5]).
URhAl and UCoAl both belong in the UTX family of compounds. This family of compounds can be divided to two: one which crystallize in hexagonal ZrNiAl structure and other which crystallize in orthorhombic TiNiSi structure. Hexagonal UTX compounds exhibit strong magnetocrtystalline anisotropy with the c-axis being the easy direction. Most of these compounds can be characterized as weak itinerant ferromagnets. One of these compounds is UCoGa with previously reported Tc = 48 K [6].
We prepared single crystals of UCoGa and investigate the influence of thermal history on its magnetic and transport properties. High quality crystal underwent pressure experiments to reach and investigate the vicinity of TCP. We will presents results obtained by magnetic and electric transport measurements in ambient and hydrostatic pressure and resulting pressure dependent magnetic phase diagram (p-T) of UCoGa.
This work is a part of the research program GACR 16-06422S which is financed by the Czech Science Foundation. Experiments were performed in the Magnetism and Low Temperature Laboratories, which is supported within the program of Czech Research Infrastructures, project no. LM2011025.
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