Work

Macroscopic ferromagnetic dynamics

Year: 2025

Type: article

Abstract: In metals with finite magnetization M→, experiment shows that transverse polarized dc spin currents J→i both decay and precess on crossing a finite sample thickness. The present work uses Onsager’s irreversible thermodynamics, with M→ and J→i as fundamental variables, to develop a theory with aspects of the Landau–Lifshitz theory solely for the M→ of (charged) electronic ferromagnets, and of the Leggett theory for the M→ and J→i of (uncharged) nuclear paramagnets. As for the ferromagnet of Landau–Lifshitz, ∂tM→ includes a characteristic decay time τM. As for the nuclear paramagnet, ∂tJ→i includes a characteristic decay time τJ, is driven by the gradient of a (vector) spin pressure, and precesses about a mean-field proportional to M→. The spin pressure has a coefficient G proportional to a velocity squared, and D0≡12GτJ serves as an effective diffusion coefficient. These equations apply when spin currents are generated. Using the derived dynamical equations for the magnetization and for the spin current, we obtain the steady-state (dc limit) solution whose transverse wavevector squared is complex, with real part from diffusion and imaginary part from precession. The ac case is also considered.

Source: Journal of Applied Physics

DOI: 10.1063/5.0291439

Authors: Chen Sun, Wayne M. Saslow

Institutions: Hunan University, Texas A&M University

Language: English

Topic: Magnetic properties of thin films

Subfield: Atomic and Molecular Physics, and Optics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: hybrid

Estimated APC paid: $3,500

Funders: National Natural Science Foundation of China, Fundamental Research Funds for the Central Universities, Fundamental Research Funds for Central Universities of the Central South University