Spin-wave resonance in a ferromagnetic metal

Abstract

The spin-wave resonance studied in this paper is a modified ferromagnetic resonance which is strongly influenced by the exchange interactions existing in the akin depth. Experimental observations of this resonance are reported, the underlying physical conditions are explained and a general "exchange boundary condition" is formulated and derived. A description is given of an experimental method for measuring both components of the complex equivalent permeability. Static measurements as well as resonance curves at 3000 and 4000 Mc/s are presented for monocrystalline and polycrystalline samples of a nickel-iron alloy having extremely low magnetocrystalline anisotropy. At room temperature the complete experimental resonance curves can be interpreted on the basis of the theory of Ament and Rado by using an effective exchange stiffness constant, A, of (3.3±0.5) × 10-6 erg/cm and a spectroscopic splitting factor, g, of 2.06±0.01. The agreement between theory and experiment would be destroyed if a Landau-Lifshitz or Bloch damping term were included. Possible processes influencing the value of A are discussed. Experimental data taken at liquid-nitrogen temperature show an increase in the resonance line width and a decrease in the resonance field. Both effects are in qualitative but not quantitative agreement with the theory. A part of the discrepancy can be attributed to anomalous effects caused by the electronic mean free path. © 1959.