Theory of transverse spin dynamics in a polarized Fermi liquid and an itinerant ferromagnet

Journal Article · Sat Oct 01 04:00:00 EDT 2005 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PhysRevB.72.144418· OSTI ID:20719617

Mineev, V P ^[1]

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1. Commissariat a l'Energie Atomique, DSM/DRFMC/SPSMS, 38054 Grenoble (France)

Linear equations for the transverse spin dynamics in a weakly polarized degenerate Fermi liquid are derived from the Landau-Silin phenomenological kinetic equation with a general two-particle collision integral. Unlike a previous treatment where the Fermi velocity and density of states were taken to be constant independent of polarization we make no such assumption. The equations found describe the spin dynamics in a paramagnetic Fermi liquid with finite polarization as well in an itinerant ferromagnet. The results are confirmed by field theoretical calculations based on the integral equation for the vertex function. The transverse spin wave frequency in a polarized paramagnetic Fermi liquid is found to be proportional to k{sup 2} with a complex diffusion coefficient such that the damping has a finite value proportional to the quasiparticles scattering rate at T=0. This behavior of a polarized Fermi liquid contrasts with the behavior of a Heisenberg ferromagnet in the hydrodynamic regime where the transverse spin-wave attenuation appears in terms proportional to k{sup 4}. The reactive part of the diffusion coefficient in a paramagnetic state at T=0 proves to be inversely proportional to the magnetization whereas in a ferromagnetic it is directly proportional to the magnetization. The dissipative part of the diffusion coefficient at T=0 in the paramagnetic state is polarization independent, whereas in the ferromagnetic state it is proportional to the square of the magnetization. Moreover, the spin wave spectrum in a ferromagnetic Fermi liquid proves to be unstable demonstrating the difficulty of applying a Fermi liquid description to itinerant ferromagnetism.

• OSTI ID: 20719617
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Journal Name: Physical Review. B, Condensed Matter and Materials Physics Journal Issue: 14 Vol. 72; ISSN 1098-0121
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ATTENUATION
COLLISION INTEGRALS
DAMPING
DENSITY
DIFFUSION
FERMI GAS
FERROMAGNETISM
HEISENBERG MODEL
INTEGRAL EQUATIONS
KINETIC EQUATIONS
MAGNETIZATION
PARAMAGNETISM
POLARIZATION
QUASI PARTICLES
SCATTERING
SPIN
SPIN WAVES
VERTEX FUNCTIONS