Abstract
The ferromagnetic resonance intrinsic field linewidth ΔH is investigated for a multilayer system such as a coupled trilayer and a spin valve structure. The magnetic coupling between two ferromagnetic layers separated by a nonmagnetic interlayer will be described by the bilinear J1 and biquadratic J2 coupling parameters. The interaction at the interface of the first ferromagnetic layer with the antiferromagnetic one is account for by the exchange anisotropy field, HE. A general formula is derived for the intrinsic linewidth ΔH. The explicit dependence of ΔH with HE, J1 and J2 will be highlighted. Analytical expressions for each mode field linewidth are found in special cases. Equivalent damping constants will be discussed.
Highlights
Ferromagnetic Resonance (FMR) spectra were investigated for coupled trilayers, i.e, two ferromagnetic layers separated by a non magnetic one, ever since the discovery of the magnetic coupling up to the present days.[5,6,7,8,9,10,11,12,13,14]
General formula for the intrinsic linewidth ∆H has been derived for coupled layers and spin valve structures
The magnetic coupling did not affect much the optical mode field linewidth but led to a large decrease of the acoustic mode one; the exchange anisotropy field HE increased the linewidth for both modes with a larger increase for the optical mode than for the acoustic one
Summary
Ferromagnetic Resonance (FMR) is a powerful method which has been widely used to investigate a variety of magnetic systems.[1,2,3,4] FMR spectra were investigated for coupled trilayers, i.e, two ferromagnetic layers separated by a non magnetic one, ever since the discovery of the magnetic coupling up to the present days.[5,6,7,8,9,10,11,12,13,14] The interest in spin valve systems (the trilayer with the addition of an antiferromagnetic layer) has increased lately;[15,16] FMR modes of spin valve have been worked out both theoretically and experimentally.[17,18,19,20] Besides the number, the positions and the intensity of the peaks appearing in a FMR spectrum, the linewidth is another interesting feature in FMR investigation. For a simple system such as a single thin film and when using the absorption curve, the intrinsic linewidth has a linear variation with the frequency and is given (for a saturated sample) by.
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