Ultrasound investigations of orbital quadrupolar ordering inUPd3

Abstract

For a high-quality single crystal of UPd 3 we present the relevant elastic constants and ultrasonic attenuation data. In addition to the magnetic phase transition at T 2 ϭ4.4Ϯ0.1 K and the quadrupolar transition at T 1 ϳ6.8 K, we find orbital ordering at T 0 ϭ7.6Ϯ0.1 K concomitant with a symmetry change from hexagonal to orthorhombic. A striking feature is the splitting of the phase transition at T 1 into a second-order transition at T ϩ1 ϭ6.9Ϯ0.05 K and a first-order transition at T Ϫ1 ϭ6.7Ϯ0.05 K. For the four phase transitions, the quadrupolar order parameters and the respective symmetry changes are specified.

Structural properties, magnetic order and electronic transport in single crystalline UPt2Si2

“…Secondly, by subsequently improving the process of material production, handling and characterization an attempt is made to identify the intrinsic properties of the ''perfect'' compound [36][37][38][39][40][41][42][43]. For this, preferably single crystalline materials should be studied.…”

Low temperature ultrasonic investigation of ZnSe crystals doped with Ni

“…Anomalies of elastic moduli and absorption of ultrasound in the vicinity of a phase transition are observed very often (see, for example, [12,13]). However, what we have observed in ZnSe:Ni could scarcely be explained only as the result of a phase transition.…”

Understanding the quadrupolar structures of

“…A range of microscopic [5][6][7] and macroscopic [8][9][10] experimental studies of UPd 3 have shown clear evidence of four phase transitions at T 0 ¼ 7:8 K, T þ1 ¼ 6:9 K, T À1 ¼ 6:7 K and T 2 ¼ 4:4 K, which we have attributed to a succession of quadrupolar ordered phases. Whilst indirect evidence of quadrupolar order was deduced some years ago from PND measurements in a magnetic field [6], the first direct microscopic evidence for quadrupolar ordering was obtained by resonant X-ray diffraction studies [7].…”