High-pressure studies of DyB 2 C 2

We performed single-crystal neutron diffraction experiments and electrical resistivity measurements under high pressure on DyB 2 C 2 showing both the antiferroquadrupolar (AFQ) and antiferromagnetic (AFM) orders. The Néel temperature T N increases gradually with increasing pressure and saturates at pressures above 5.2 GPa while the AFQ transition temperature T Q decreases almost monotonically up to 3.13 GPa and seems to merge with T N at around 6–7 GPa. These results indicate that the application of pressure suppresses the AFQ ordering in DyB 2 C 2 and simultaneously enhances the AFM interaction between 4 f spins. The suppression of the AFQ ordering can be interpreted as being due to the restriction of the local strain associated with the AFQ transition caused by applying pressure.