Magnetic properties of HoBC under high pressure; A Single-crystal neutron diffraction study

Yamauchi, Hiroki   ; Osakabe, Toyotaka  ; Matsuoka, Eiichi*; Onodera, Hideya*

We carried out single-crystal neutron diffraction experiments under high pressure on HoBC showing both of the antiferroquadrupolar (AFQ) and antiferromagnetic (AFM) orders to clarify the pressure effects on the competitive AFQ + AFM order through the alteration of the magnetic structure represented by = (1, 0, 0) and = (0, 1, 1/2). The high-pressure experiments reveal that the AFQ ordering in HoBC is extremely pressure sensitive and is suppressed by pressure below 4 GPa whereas the pressure enhances the AFM interactions up to 9.8 GPa. The suppression of the AFQ ordering can be interpreted as being due to the restriction of the local strain associated with the AFQ transition by applying pressure. Above 4 GPa, we find the new pressure-induced phases, phase AFM1 and AFM2, where HoBC transforms into the magnetic structures represented by + ( = (1 + , , 0), 0.1) and , respectively.