Magnetic fluctuations and the spin-orbit interaction in Mott insulating CoO.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Magnetism

Background:

• Cobalt Oxide (CoO) is a classic Mott insulator with unquenched orbital angular momentum, posing challenges for understanding its magnetic properties.
• Early inelastic neutron scattering experiments in 1968 identified magnon modes but failed to parameterize the low-energy magnetic excitation spectrum.
• The discovery of high-temperature cuprate superconductors motivated renewed interest in complex magnetic systems like CoO.

Purpose of the Study:

• To re-investigate and successfully parameterize the complex magnetic excitation spectrum of Cobalt Oxide (CoO).
• To determine fundamental single-ion and cooperative magnetic parameters for CoO.
• To utilize a spin-orbit exciton model for a comprehensive description of CoO's magnetic behavior.

Main Methods:

• Performed inelastic neutron scattering experiments on CoO and a dilute analogue Mg$_{0.97}$Co$_{0.03}$O in the early 2010s.
• Determined single-ion magnetic parameters (Cowley et al. 2013) and cooperative magnetic parameters (Sarte et al. 2018).
• Employed a spin-orbit exciton model (Sarte et al. 2019) using the determined parameters.

Main Results:

• Successfully determined crucial single-ion and cooperative magnetic parameters for CoO.
• The spin-orbit exciton model, utilizing these parameters, accurately parameterized the complex magnetic excitation spectrum.
• This resolved a long-standing challenge in understanding CoO's magnetic dynamics, first observed nearly 50 years prior.

Conclusions:

• The study successfully parameterized the magnetic excitation spectrum of CoO, overcoming previous limitations.
• The determined magnetic parameters and the spin-orbit exciton model provide a comprehensive understanding of CoO's magnetic behavior.
• This work highlights the interplay of experimental advancements and theoretical modeling in resolving complex condensed matter phenomena.