Tricritical point of the f -electron antiferromagnet USb2 driven by high magnetic fields

Abstract

In pulsed magnetic fields up to 65T and at temperatures below the Néel transition, our magnetization and magnetostriction measurements reveal a field-induced metamagnetic-like transition that is suggestive of an antiferromagnetic to ferrimagnetic ordering. Our data also suggests a change in the nature of this metamagnetic-like transition from second-to first-orderlike near a tricritical point at T tc ~145K and H c~5 2T. At high fields for H>H c we found a decreased magnetic moment roughly half of the moment determined by neutron powder diffraction. We propose that the decreased moment and lack of saturation at high fields indicate the presence of a field-induced ferrimagnetic state above the tricritical point of the H-T phase diagram for USb 2 .

High temperature singlet-based magnetism from Hund’s rule correlations

“…Uranium compounds can feature a fascinating interplay of strongly correlated and itinerant electronic physics, setting the stage for emergent phenomena such as quantum criticality, heavy fermion superconductivity, and elusive hidden order states [1][2][3][4][5][6][7][8][9][10][11][12][13]. The isostructural uranium dipnictides UX 2 (X=As, Sb, Bi) present a compositional series in which high near-neighbor uranium-uranium coordination supports robust planar antiferromagnetism (T N~2 00K, see Fig.…”

“…1a-b) [7,8]. Of these, the USb 2 variant has received close attention due to the discovery of several unexplained low temperature quantum coherence phenomena at T<100K [7,9,10,11], and a remarkably rich phase diagram incorporating quantum critical and tricritical points as a function of pressure and magnetic field [12,13]. However, the effective valence state of uranium and the resulting crystal field state basis defining the f-electron component of local moment and Kondo physics have not been identified.…”

Magnetic field induced antiferromagnetic tricritical points in Ce2Sb and Ce2Bi

“…At low temperatures, the magnetization at 5 T corresponds to 1.05 µ B /Ce and 0.935 µ B /Ce for Ce 2 Sb and Ce 2 Bi respectively. In the case of USb 2 , it could be determined that the jump in magnetization at the metamagnetic transition corresponded to just half of the saturated value from a comparison with neutron diffraction results 14,26 , which indicates that the spins are not fully aligned in the high field state. However, for Ce 2 Sb and Ce 2 Bi, we are not able to determine if the magne- tization at 5 T corresponds to the full value of the Ce moments and therefore whether the system is in the spin polarized state .…”

“…This ultimately gives rise to a TCP at the termination of the first-order line separating the new magnetic ground state and the field-induced FM phase. On the other hand, the occurrence of TCPs in AFM systems is somewhat less common, although a high field study of USb 2 revealed a TCP between the AFM ground state and a field-induced ferrimagnetic phase 14 . In some systems, the position of the TCP can be tuned by pressure or doping, which can allow for the continuous suppression of the TCP to zero temperature at a quantum tricritical point (QTCP).…”

Fiber Bragg Grating Dilatometry in Extreme Magnetic Field and Cryogenic Conditions

“…Sensing of magnetostriction with single mode SiO 2 FBGs in pulsed magnetic fields is successfully utilized at the National High Magnetic Field Laboratory (NHMFL) with a resolution as good as a few parts per hundred million ( ΔL/L ≈ 10 −8 ) in the best cases. This capability allows for the study of a variety of insulating and metallic condensed matter systems including geometrically frustrated magnets, quantum magnets, multiferroics, and uranium- and cerium-based antiferromagnets [6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30]. Figure 1 shows an example of magnetoelastic effects in pulsed magnetic fields to 60 T at cryogenic temperatures on a sample of uranium dioxide (UO 2 ), which is the most commonly used nuclear fuel.…”