Physical properties of semimetallic magnets UOX (X = S, Se, Te)

Opletal, P.  ; 酒井 宏典   ; 常盤 欣文  ; 芳賀 芳範   ; 山本 悦嗣  ; 神戸 振作  ; 徳永 陽  

Opletal, P.; Sakai, Hironori; Tokiwa, Yoshifumi; Haga, Yoshinori; Yamamoto, Etsuji; Kambe, Shinsaku; Tokunaga, Yo

Uranium chalcogenides are large group of compounds showing different interesting properties. We will mainly discuss three different representatives: UTe, UOX (X= S, Se, Te) and UTe. UTe recently gained large research interest due to discovery of unusual superconductivity and possible existence of topological spin-triplet conductivity. We managed to prepare highest quality of single crystals yet by molten salt growth method which shows almost doubled critical field for a-axis. To better understand superconductivity and physical properties of UTe we investigate change of magnetic property in magnetic field for all the crystallographic direction. We will compare and discuss our results on molten-salt grown sample UTe to results in literature. We will show that magnetic entropy at high temperatures, well above superconductivity, shows connection to superconducting properties. UOX (X= S, Se, Te) is group of antiferromagnets with high Neel temperature (80 K - 158 K). UOTe was predicted to be possibly Weyl semimetal. We prepared single crystal of these compounds by chemical vapor transport. All three compounds show semimetallic behavior with UOTe showing additional anomalies. We will present our results and discuss coexistence of small conductivity and high Neel temperature and possible non-trivial topological effects. UTe crystallizes in hexagonal structure P-6 with three different uranium positions and orders ferromagnetically at 48 K. It show additional increase of magnetization around 26 K in hard magnetic direction and behaves as semimeta. We will present our results and discuss possible origin of additional ordering in hard magnetic direction based on crystal structure and its connection to semimetallic behavior. We want to show that uranium chalcogenides are large group in which different phenomena can be observed due to different level of localization of uranium 5f level states.