Field-Induced Magnetic Structures in Antiferroquadrupolar Ordering Compound DyB₂C₂

Abstract

Neutron scattering experiments were performed on the single-crystalline DyB₂C₂ under magnetic fields in order to elucidate the magnetic structures of field-induced phases. The measurements in the a^*–c^* reciprocal lattice plane under the magnetic fields along the [010] direction resulted in finding a new magnetic reflection of 1 0 3⁄4 in a field-induced phase (phase II^′′) in addition to the magnetic reflections that are common to those in the phase under a zero magnetic field (phase III). The magnetic unit cell in phase II^′′ has dimensions of a×a×4c, where all the Dy magnetic moments on the AFQ structure have advantageous directions to the magnetic field, and their AFQ couplings with the neighbouring moments along the c-axis are partly broken. This magnetic structure model for phase II^′′ well explains the magnetisation process at 5 K up to 14 T.