Magnetic-Field-Induced Quadrupolar Ordering And The Crystal Electric Field Effect In The Distorted Kagome Lattice Antiferromagnet Dy3ru4al12

To investigate the 4f-electronic states under a crystal electric field (CEF) and the phase transition in Dy3Ru4Al12 with the antiferromagnetic transition temperature T-N = 7 K, we performed ultrasonic measurements on a single-crystalline sample at zero magnetic field and under fields. The transverse elastic modulus C-44 shows a characteristic elastic softening. The CEF analyses indicate that the softening is caused by an interlevel quadrupole interaction between the ground and excited Kramers doublets. Under fields, we found a magnetic-field-induced phase transition along both the [100] and [001] directions in addition to the antiferromagnetic ordering. Aplausible origin of the field-induced transition is quadrupolar ordering, which is estimated from our CEF calculation. These results and the negative sign of a quadrupole-quadrupole coupling constant suggest that the effect of geometrical frustration alignment due to the kagome lattice also appears on the electric quadrupoles of the Dy ions with the antiferroquadrupolar-type interaction.