Antiferromagnetism and phase transitions in noncentrosymmetric UIrSi3

Abstract

Magnetization and specific heat measurements on a UIrSi 3 single crystal reveal Ising-like antiferromagnetism below T N = 41.7 K with easy magnetization direction along the c-axis of tetragonal structure. The antiferromagentic ordering is suppressed by magnetic fields > H c (µ 0 H c = 7.3 T at 2 K) applied along the c-axis. The first-order metamagnetic transition at H c 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 T tc = 28 K and µ 0 H tc = 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,  p a ~ -51 K and  p c ~ +38 K, respectively. This result and the small value of µ 0 H c contrasting to the high T N indicate competing ferromagnetic and antiferromagnetic interactions responsible for the complex antiferromagnetic ground state. The simultaneous electronic-structure calculations focused on the total energy of ferromagentic 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.

Hydrogen induced structure and property changes in Eu3Si4

“…The magnetization as a function of field behavior at 6 K is complex and exhibits a second magnetic hysteresis loop at high fields (above 3000 kA/m), see Figure 9b). A similar behavior to the data presented in Figure 9b has been observed in single crystals of the antiferromagnet UIrSi3, which crystallizes in the tetragonal BaNiSn3 structure type [33]. The magnetic moments in UIrSi3 order ferromagnetically in the ab plane with the moments aligned along the c axis.…”

Magnetic field induced phenomena in UIrGe in fields applied along the b axis

“…Experimental studies concerning tricriticality in antiferromagnets are quite rarely reported in literature although understanding of these phenomena has fundamental importance. TCPs have been reported in several uranium antiferromagnets exhibiting Ising-like behavior caused by very strong magnetocrystalline anisotropy [23][24][25][26][27] . We mark the tentatively considered TCP in the magnetic phase diagram in Fig.…”

Magnetic phase diagram of the antiferromagnet U2Rh2Pb

“…In previously studied AFM materials [41][42][43], the disappearance of the hysteresis has been considered as one of the signatures of a tricritical point (TCP) in the phase diagram which separates first-and second-order AFM transitions and exhibiting Ising-type anisotropy [42,[44][45][46][47]. This supports the existence of TCP in U2Rh2Pb around Ttc = 13 K and µ0Htc = 4 T. It should be pointed out that TCP is an inherent feature of a broad class of antiferromagnets, in which the metamagnetic transition at low temperatures is of the first-order type and magnetic critical point in zero field is of the second-order type, and hence does now imply any temperature variations of magnetic interactions [48].…”