Valenta, J., Honda, F., Valiska, M., Opletal, P., Kastil, J., Misek, M., Divis, M., Sandratskii, L. M., Prchal, J., Sechovsky, V.
Antiferromagnetism and phase transitions in noncentrosymmetric UIrSi3
Physical Review B 97, (14),pp 144423/1-8 (2018)
Magnetization and specific-heat measurements on a UIrSi3 single crystal reveal Ising-like antiferromagnetism below TN = 41.7K with the easy magnetization direction along the c axis of the tetragonal structure. The antiferromagnetic ordering is suppressed by magnetic fields > Hc (μ0Hc = 7.3 T at 2 K) applied along the c axis. The first-order metamagnetic transition at Hc exhibits asymmetric hysteresis reflecting a slow reentry of the complex ground-state antiferromagnetic structure with decreasing field. The hysteresis narrows with increasing temperature and vanishes at 28 K. A second-order metamagnetic transition is observed at higher temperatures. The point of change of the order of transition in the established H-T magnetic phase diagram is considered as the tricritical point (at Ttc = 28 K and μ0Htc = 5.8 T). The modified-Curie-Weiss law fits of temperature dependence of the a- and c-axis susceptibility provide opposite signs of Weiss temperatures, Θap ∼ -51K and Θcp ∼ +38K, respectively. This result and the small value of μ0Hc contrasting to the high TN indicate competing ferromagnetic and antiferromagnetic interactions responsible for the complex antiferromagnetic ground state. The simultaneous electronic-structure calculations focused on the total energy of ferromagnetic and various antiferromagnetic states, the U magnetic moment, and magnetocrystalline anisotropy provide results consistent with experimental findings and the suggested physical picture of the system.
TH-2018-13