Goldstone modes of incommensurate chromium alloys

R. S. Fishman; S. H. Liu

doi:10.1063/1.361620

Goldstone modes of incommensurate chromium alloys

R. S. Fishman, S. H. Liu

Materials Theory

University of California at San Diego

Research output: Contribution to journal › Article › peer-review

Abstract

The spin excitations about the two incommensurate wavevectors of the spin-density-wave (SDW) state in Cr are studied for the first time within the random-phase approximation. Transverse spin-wave (SW) modes and longitudinal phason modes are associated with the rotational and translational symmetries of Cr. While both mode frequencies vanish at the SDW ordering wavevectors, only the SW mode with linear dispersion and mode velocity c = υ_F/√3 is undamped for nonzero frequencies. As in a local-moment system, the SW mode corresponds to the rigid rotation of the local magnetic moments. The phason modes have a nearly linear dispersion at low frequencies with velocity c_phc. As T approaches T_N, c_ph approaches c. Phason modes have been observed in the longitudinally polarized SDW state below 120 K in pure Cr and are responsible for a 60 meV peak in the cross sections midway between the satellites.

Original language	English
Pages (from-to)	4824-4826
Number of pages	3
Journal	Journal of Applied Physics
Volume	79
Issue number	8 PART 2A
DOIs	https://doi.org/10.1063/1.361620
State	Published - Apr 15 1996

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AB - The spin excitations about the two incommensurate wavevectors of the spin-density-wave (SDW) state in Cr are studied for the first time within the random-phase approximation. Transverse spin-wave (SW) modes and longitudinal phason modes are associated with the rotational and translational symmetries of Cr. While both mode frequencies vanish at the SDW ordering wavevectors, only the SW mode with linear dispersion and mode velocity c = υF/√3 is undamped for nonzero frequencies. As in a local-moment system, the SW mode corresponds to the rigid rotation of the local magnetic moments. The phason modes have a nearly linear dispersion at low frequencies with velocity cphc. As T approaches TN, cph approaches c. Phason modes have been observed in the longitudinally polarized SDW state below 120 K in pure Cr and are responsible for a 60 meV peak in the cross sections midway between the satellites.

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Goldstone modes of incommensurate chromium alloys

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