Anisotropic physical properties of single-crystal U2Rh2Sn in high magnetic fields

Abstract

We report on the crystal and magnetic structures, magnetic, transport and thermal properties of U 2 Rh 2 Sn single crystals studied in part in high magnetic fields up to 58 T. The material adopts a U 3 Si 2 -related tetragonal crystal structure and orders antiferromagnetically below T N = 25 K. The antiferromagnetic structure is characterized by a propagation vector k = (0 0 1 2 ). The magnetism in U 2 Rh 2 Sn is found to be associated mainly with 5f states. However, both unpolarized and polarized neutron experiments reveal at low temperatures in zero field non-negligible magnetic moments also on Rh sites. U moments of 0.50(2) µ B are directed along the tetragonal axis while and Rh moments of 0.06(4) µ B form a non-collinear arrangement confined to the basal plane. The response to applied magnetic field is highly anisotropic. Above ∼ 15 K the easy magnetization direction is along the tetragonal axis. At lower temperatures, however, a stronger response is found perpendicular to the c axis. While for the a axis no magnetic phase transition is observed up to 58 T, for the field applied at 1.8 K along the tetragonal axis we observe above 22.5 T a field-polarized state. A magnetic phase diagram for the field applied along the c axis is presented.

Acoustic signatures of the phase transitions in the antiferromagnet U2Rh2Sn

“…3(a)]. The broader character of the anomaly at higher temperatures corresponds to a broader jump in the magnetization [12]. Above T N = 25 K, the phase transition is no longer observed in v/v.…”

“…A U 2 Rh 2 Sn single crystal was prepared by a modified Czochralski method as described in Ref. [12]. The lattice parameters of the tetragonal crystal structure (space group P4/mbm) are a = 7.449(1) Å and c = 3.586(1) Å. Backscattered Laue diffraction was used to check the singlecrystalline state and to orient the crystal for magnetization, specific-heat, and ultrasound measurements.…”

“…No anomalies are observed for field applied in the basal plane. Neutron scattering shows that the uranium moments align along the [001] axis, while the rhodium moments form a noncollinear arrangement in the basal plane [12]. For isostructural U 2 Ni 2 Sn, the [001] axis is also the easy magnetization direction [9].…”

“…Consequently, the magnetic moments align along the c axis [9]. For U 2 Rh 2 Sn, however, the shortest U-U distances, 3.586 Å, are along the c axis, while those in the basal plane are 3.622 Å [10][11][12]. Nevertheless, the uranium moments also align along the c axis.…”

“…Here, one may compare isostructural U 2 Ni 2 Sn and U 2 Rh 2 Sn. Both materials are antiferromagnets below the Néel temperature, T N = 25 K [4][5][6][7][8][9][10][11][12][13][14][15][16]. For U 2 Ni 2 Sn, the U-U distances within the basal plane of a tetragonal crystal structure, 3.575 Å, are substantially shorter than those along the c axis, 3.693 Å [4,6,11].…”