Magnetic neutron scattering study of single-crystal cupric oxide

Abstract

Among ${\mathrm{Cu}}^{2+}$ compounds, cupric oxide (CuO) has unusual magnetic properties, some of which are shared by the superconducting copper oxides. In order to study these properties further, neutron scattering experiments on a CuO single crystal have been performed. Two magnetic phase transitions at ${T}_{N1}$=231 K and ${T}_{N2}$=212.5 K have been observed, with the magnetic structure below ${T}_{N2}$ antiferromagnetic and the structure between ${T}_{N1}$ and ${T}_{N2}$ helical in nature. The dynamics of the magnetism was also studied. As in ${\mathrm{La}}_{2}$${\mathrm{CuO}}_{4}$, the dispersion of the low-temperature spin-wave excitations is unusually steep (dE/dk=250\ifmmode\pm\else\textpm\fi{}75 meV A${\r{}}^{\mathrm{\ensuremath{-}}1}$), indicating strong magnetic interactions. Inelastic magnetic scattering has also been measured above ${T}_{N1}$. At temperatures slightly above the 231-K phase transition, dynamic critical slowing has been observed.