High pressure neutron diffraction investigation of CuO

Abstract

The dependence of the magnetic structure of CuO on hydrostatic pressureup to 18 kbar has been studied by means of neutron diffraction at lowtemperatures. The pressure dependences of both the Néel temperatureTN and the incommensurate–commensurate lock-in transition temperatureTL have been determined. The Néel temperature, which is 230 K at ambient pressure, increases toTN = 235 K atP = 18 kbar,whereas the lock-in transition temperature, which is 213 K at ambient pressure, decreases continuouslyto TL = 207 Kat P = 18 kbar. Since hydrostatic pressure increases the stability range of the incommensurate phase,it is likely that at very high pressures the incommensurate phase would be the only stableordered magnetic phase of CuO and the commensurate antiferromagnetic phase would becompletely suppressed.