Spin dynamics and exchange interactions in CuO measured by neutron scattering

Abstract

The magnetic properties of CuO encompass several contemporary themes in condensed matter physics, including quantum magnetism, magnetic frustration, magnetically-induced ferroelectricity and orbital currents. Here we report polarized and unpolarized neutron inelastic scattering measurements which provide a comprehensive map of the cooperative spin dynamics in the low temperature antiferromagnetic (AFM) phase of CuO throughout much of the Brillouin zone. At high energies (E 100 meV) the spectrum displays continuum features consistent with the des Cloizeax-Pearson dispersion for an ideal S = 1 2 Heisenberg AFM chain. At lower energies the spectrum becomes more three-dimensional, and we find that a linear spin-wave model for a Heisenberg AFM provides a very good description of the data, allowing for an accurate determination of the relevant exchange constants in an effective spin Hamiltonian for CuO. In the high temperature helicoidal phase, there are features in the measured low-energy spectrum that we could not reproduce with a spin-only model. We discuss how these might be associated with the magnetically-induced multiferroic behavior observed in this phase.

Potential room-temperature multiferroicity in cupric oxide under high pressure

“…To our knowledge, the experimental pressure dependence of the J ij exchange interactions has not been reported, so far. We will thus compare our calculations with the ambient pressure neutron scattering experimental data [34], as summarized in Table I. The authors applied constraints to simplify their Hamiltonian, leading to differences with our Hamiltonian.…”

Magnons in the Multiferroic Phase of Cupric Oxide

“…Moreover, there is evidence for some individual modes for energies near 3, 9, and 14 meV, in particular, which could not be resolved in the Jacobsen experiment. The present data are, however, not yet sufficient to improve the spin dynamics models of Gaw [32] or Jacobsen et al [20]…”

“…Parallel to our own study, Jacobsen et al independently performed similar experiments using conventional methods of polarized neutron scattering. They were able to determine details of the exchange interactions, and their results are consistent with our own findings.…”

“…Because magnon branches are extremely steep in the AF1 phase [14][15][16][17] as well as in the AF2 phase, [20] it is not possible to resolve the q dependence of the magnon energy close to the magnetic zone center at q C/IC . A constant energy scan leads to a broad intensity distribution with the center at the position of the superlattice reflection and an increasing half-width at higher energies.…”

Momentum-Dependent Magnon Lifetime in the Metallic Noncollinear Triangular Antiferromagnet CrB2

“…2 and 3). Note that these resolution effects can be precisely calculated by our analysis using TobyFit, which fully takes into account a complex resolution ellipsoid of a real experiment [26][27][28] (see Fig. S4 [20]).…”