Spin and orbital ferromagnetism in strongly correlated itinerant electron systems

TL;DR

This paper investigates the spectra of excitations in narrow-band ferromagnets with unquenched orbital moments, revealing the coexistence of well-defined orbitons and small damping effects, and discusses stability criteria and potential orbital ordering effects.

Contribution

It introduces theoretical models analyzing spin and orbital excitations, highlighting the existence of orbitons and non-quasiparticle states in strongly correlated electron systems.

Findings

Existence of well-defined orbitons in narrow-band ferromagnets.

Small damping of spin and orbital excitations due to electron interactions.

Criteria for stability of spin and orbital ferromagnetic order.

Abstract

Spectra of one-electron and collective excitations in narrow-band ferromagnets with unquenched orbital moments are calculated in various theoretical models. The interaction of spin and orbital excitations with conduction electrons results in the damping of the former which, however, turns out to be rather small; therefore, apart from usual spin waves, well-defined orbitons can exist. Non-quasiparticle states occur in the electron energy spectrum near the Fermi energy due to this interaction. The criteria of stability of the saturated spin and orbital ferromagnetic ordering are considered. Possible effects of orbital ordering in magnetite and in colossal magnetoresistance manganites are discussed.