Intrinsic damping and intentional ferromagnetic resonance broadening in thin Permalloy films

Abstract

Detailed ferromagnetic resonance measurements on thin Ni80Fe20 films are described that determine characteristics of intrinsic damping and the effects of intentionally created defects on linewidth. Measurements are made as a function of frequency with magnetization oriented in-plane and normal to the plane. For nominally uniform films, the ferromagnetic resonance linewidth is linear in frequency for both in-plane and normal magnetization and is well described by Landau–Lifshitz damping with a constant damping parameter. The effect of inhomogeneity was investigated by depositing the Ni80Fe20 films on specially prepared substrates, one with parallel, random grooves and one with polycrystalline, antiferromagnetic NiO. The linewidth in these samples is generally larger with magnetization in-plane than it is with magnetization normal. In the NiO/Ni80Fe20 film, the in-plane linewidth is linear in frequency with a significant zero-frequency linewidth. In the Ni80Fe20 sample on the grooved substrate, the linewidth has a more complicated frequency dependence.

Magnetic properties in ultrathin 3d transition-metal binary alloys. II. Experimental verification of quantitative theories of damping and spin pumping

“…There are only a limited number of reports for H 0 in the literature with which to compare. For permalloy (Ni 80 Fe 20 ) we measure H 0 = 0.35 mT, which is close to other reported values [35]. For the other Ni x Fe 1−x alloys, H 0 exhibits a significant peak near the fcc-to-bcc (face-centered-cubic to body-centered-cubic) phase transition at 30% Ni [see Fig.…”

Classical Model of Extrinsic Ferromagnetic Resonance Linewidth in Ultrathin Films

“…In a number of measurements of the frequency dependence of linewidth in thin films, the data is reasonably well described by a linear relationship of this type [17], [26], [29]- [34].…”

“…As described in more detail below, for special cases where the magnetization and applied field are parallel, the LLG equations of motion (1) lead to a full width of the resonance (2) This expression is appropriate for an experiment where the spectrometer drives the magnetization at angular frequency and the transverse susceptibility is measured as a function of applied field. There are other possible phenomenological descriptions of damping that lead to other expressions for the linewidth [1], [16], but for some nominally uniform films, the linewidth is well described by the LLG form of damping [17].…”

Role of antisite disorder on intrinsic Gilbert damping inL10FePt films

“…The uniform magnetization precession can be well modeled with Landau-Lifshitz-GilbertSlonczewski (LLGS) equation [7][8][9], where the Slonczewski torque term denotes the spin transfer torques (STTs), and the Gilbert damping parameter α determines the spin relaxation time [10] and is crucial for device performance [11][12][13][14]. The extrinsic Gilbert damping is due to nonlocal spin relaxation, such as spin pumping and magnon-magnon scattering, which can be tuned by artificial substrates, specially designed buffer and coverage layers [15][16][17][18][19][20][21], while the intrinsic Gilbert damping parameter α 0 is thought to arise from spin-orbit interaction (SOI) [22][23][24][25][26][27][28][29][30], and recently its quadratic dependence on SOI is demonstrated experimentally in FePtPd alloys [31].The α 0 describes the energy flow rate from spin to electronic orbital and phonon degrees of freedom through electron scattering, and has been studied in various theoretical models [22][23][24][25][26][27][28][29][30]. The breathing Fermi surface model [22] and torque-correlation model [23] based on first principle band structure calculations qualitatively match α 0 in soft magnetic alloys such as Fe, .…”