The cooperative Jahn-Teller effect in uranium (4+) hydroxy-sulphate

Abstract

The magnetic susceptibility measurements of orthorhombic U(OH) 2SO 4 within the temperature range 4.2–300 K have revealed a magnetic anomaly at T D = 21 K associated with crystallographic transition induced by the cooperative Jahn-Teller effect. Above 21 K the magnetic susceptibility of the uranium (4+) ion corresponds to the electronic ground doublet ¡M J = ± 2〉 confirming thus the antiprismatic symmetry ( D 4d ) of the crystal field at the uranium site. Below T D the system of two singlets ( 1 √2 )|2〉 ± ( 1 √2 )| 2 〉 separated by δ( T) is the ground state of the uranium ion.