Non-magnetic to Magnetic Transition under High Pressure in Narrow-Gap Semiconductor β-US₂

Abstract

We have measured the magnetization of an uranium chalcogenide compound β-US 2 under high pressure by piston cylinder and indenter type cells up to 2.42 GPa in a commercial SQUID magnetometer. The compound is a narrow-gap semiconductor that does not order magnetically down to 0.3 K at 1 bar. The appearance of a pressure-induced phase above 2 GPa was suggested by a previous study with the electrical resistivity measurement under high pressure. In this study, it was found that a ferromagnetic state is induced above 1 GPa. The pressure phase diagram were obtained. The values of the spontaneous magnetic moment at 0 K are less than 0.1 µ B /U, suggesting that the pressure-induced phase is a very weak ferromagnetic state. Considering the CEF singlet ground state in β-US 2 , it is suggest that the ferromagnetic state is an "induced-magnetic phase" often observed in some praseodymium compounds such as Pr 3 Tl. The experimental results are discussed in terms of the mean field theory.

Analysis of Magnetization Behavior in Magnetic Semiconductor β-US2

“…High-pressure investigations on β-US 2 [6] and UTeS suggest that ferromagnetism is stabilized at high pressures. Although β-US 2 at ambient pressure is a paramagnet, it appears to be located near a ferromagnetic instability.…”

Drastic Change in Ferromagnetic Ground State Associated with Pressure-Induced Metal-Insulator Transition in β-US2

“…Previously, we found that the ferromagnetic state is induced in the semiconducting β-US 2 by the application of the pressure above the critical pressure of 0.7 GPa [13]. The pressure-induced ferromagnetic state was discussed in terms of "induced-magnetic moment state" often observed in some praseodymium compounds with the singlet ground state such as Pr 3 Tl [14].…”

33S Nuclear Magnetic Resonance Spectra of Uranium Disulfide β-US2

“…Interestingly, when a strong external field is applied, the semiconducting behavior at low temperatures is completely suppressed [5]. In addition, ferromagnetism is easily induced by a relatively low pressure of about 1 GPa [6]. Consequently, β-US 2 is considered to possess a ferromagnetic instability.…”