High-pressure studies of DyB2C2

We performed single-crystal neutron diffraction experiments and electrical resistivity measurements under high pressure on DyB2C2 showing both the antiferroquadrupolar (AFQ) and antiferromagnetic (AFM) orders. The Neel 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 DyB2C2 and simultaneously enhances the AFM interaction between 4f 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.