Quantum ferromagnet in the proximity of the tricritical point

Abstract

Echoes of quantum phase transitions at finite temperatures are theoretically and experimentally challenging and unexplored topics. Particularly in metallic quantum ferromagnets the experimental investigations are hampered by an intricate preparation of sufficiently pure samples and the access to the proper coordinates in parameter space. The present study shows that it is possible to tune a specific system at easily accessible conditions to the vicinity of its quantum phase transition. The physics is demonstrated on Ru-doped UCoAl, driven by pressure or substitution to and across the tricritical point and follows the first-order transition line to the theoretically presumed quantum phase transition. These findings open the possibilities for further in-depth studies of classical and quantum critical phenomena at easily reachable conditions.

Effect of thermal history on magnetism in UCoGa

“…This is also seen in change of critical exponent β, which differs from other crystals. If we compare the residual resistivity of the SC2A900 sample with those available in literature of other members of the UTX family with the ZrNiAl crystal structure, we see that the best values are of the order of 10 μΩ.cm (URhAl [15], UCoAl [3,16], UNiGa [17]). These values are fully comparable to the best values obtained in this study.…”

Ferromagnetic quantum criticality: New aspects from the phase diagram of LaCrGe3

“…Similar experimental studies have revealed other wing-structure phase diagrams in UGe 2 [8,30,31] (also shown in Fig. 6 for comparison), Sr 3 Ru 2 O 7 [37], ZrZn 2 [9], UCoAl [35,36,40]. The behavior near the tricritical point could not be studied in Sr 3 Ru 2 O 7 and UCoAl because those compounds are already in the paramagnetic regime at ambient pressure.…”

“…The behavior near the tricritical point could not be studied in Sr 3 Ru 2 O 7 and UCoAl because those compounds are already in the paramagnetic regime at ambient pressure. Substitutions studies revealed the existence of a nearby tricritical point in UCoAl [40]. In ZrZn 2 , the tricritical point is near 3 K, making the experimental investigations difficult.…”

Pressure evolution of magnetism in URhGa

“…The very strong uniaxial magnetic anisotropy locks the U magnetic moments aligned along the c-axis of the hexagonal structure whereas only Pauli paramagnetism is observed in the perpendicular directions. Several these compounds order ferromagnetically providing a playground for investigation of the critical behavior of itinerant ferromagnets [2][3][4][5]. Contrary to the case of antiferromagnetism where novel states are result of the presence of quantum critical point (QCP; see e.g.…”