Elastic constants of antiferro-quadrupole ordering system DyB 2C 2

Abstract

Elastic constants of tetragonal system DyB 2C 2 with antiferro-quadrupole (AFQ) ordering have been measured by using ultrasonic method. Remarkable elastic softenings of the C 44 and ( C 11− C 12)/2 have been observed towards the AFQ transition at T Q =25 K . The present results show that a CEF ground state is a pseudo-quartet consisting of two Kramers doublets of E 1/2 and E 3/2 in C 4h site symmetry of Dy 3+ ion. The dominant softening of C 44 probably leads to the order parameter of O yz and O zx in AFQ phase. Magnetic phase diagram applied fields along the [1 0 0] direction determined by field dependence of the C 44 is presented.