Magnetization Dynamics In Thin Films Research Articles

Electrical Detection of Antiferromagnetic Dynamics in Gd - Co Thin Films Using 154-GHz Gyrotron Irradiation

The ultrahigh-frequency magnetization dynamics of antiferromagnets and ferrimagnets is a key property that could be exploited for terahertz technology and spintronics. Despite recent advances in measuring bulk samples, no techniques have been available to characterize such fast dynamics in the thin films that are important for devices. In this Letter the authors use a gyrotron to demonstrate electrical detection of subterahertz magnetization dynamics in thin films, revealing peculiar antiferromagnetic behavior in Gd-Co.

Development of a technique for inductive measurement of laser-induced magnetization dynamics in thin films

Development of a technique for inductive measurement of laser-induced magnetization dynamics in thin films

Study on measurement technique for magnetization dynamics of thin films

This paper describes our proposed measurement technique for the magnetization dynamics in thin films, which employs a microstripe line probe to detect ferromagnetic resonance (FMR) spectra for a film sample either with or without tensile stress. By measurement of FMR frequency shifts using Lorentzian fits to the FMR spectra for a film with and without tensile stress, saturation magnetostriction (λs) can be determined. The measured values were compared with those estimated by the optical cantilever method using the same samples in good agreement. At the same time, a Gilbert damping constant (α) was determined using both the FMR frequency and the FMR linewidth for the tensile stress free film. The results of the experiment demonstrate that our proposed measurement technique allows for more precise evaluation of magnetization dynamics by providing information on both α and λs simultaneously for an individual sample.

Landau-Lifshitz equation for magnetization dynamics of thin films: Failure of the linear approximation at low effective fields

We have obtained numerical solutions of the Landau-Lifshitz equation for the nonlinear response of a monodomain uniaxial ferromagnetic thin film subjected to static longitudinal and sinusoidal transverse in-plane magnetic fields with the easy axis exactly or nearly transverse to the static field. For transverse anisotropy, the well-known linear approximation predicts that the ferromagnetic resonance frequency goes to zero when the longitudinal field is equal to the anisotropy field, that is, when the static internal field goes to zero. This is not correct for nonzero sinusoidal fields. At low resonance frequency, the resonance field is less than the anisotropy field. This shift increases as the ac field is increased. The difference between the linear and nonlinear values of resonance frequency for a given static field is explained in terms of switching times shorter than the period at low frequency.

Ultrafast Tuning of Magnetization Precession and Magnetic Anisotropy in Thin Iron Films

AbstractWe have developed an experimental set-up based on time-resolved Magneto-Optical Kerr Effect (MOKE) that allows to retrieve the vectorial magnetization dynamics in thin films with sub-picosecond resolution. This method has been exploited to measure the variations of the magnetization (modulus and orientation) induced by an ultrashort laser pulse. The initial demagnetization is established at the electronic level within a few hundreds of femtoseconds through electron-magnon excitations. The subsequent dynamics is characterized by a precessional motion on the 100 picosecond time-scale, around an effective, time-dependent field. Following the full dynamics of the magnetization, we have unambiguously determined the temporal evolution of the magneto-crystalline anisotropy, providing the clear experimental evidence that the precession is triggered by the rapid, optically-induced misalignment between the magnetization vector and the effective field. This method provides a simple and widely applicable way to study both magnetization and anisotropy in the sub-picosecond regime and therefore to unravel the mechanisms underlying the ultrafast evolution of the spin order in magnetic media.

Magnetization dynamics in thin films and multilayers

The behavior of spin waves is influenced by essentially all the parameters which characterize a magnetic material – exchange interactions, anisotropy, surface effects, dipolar interactions, phase transitions and imperfections. Thus measurements of spin wave frequencies can give important information on characterizing different magnetic materials and structures. In this paper we outline the major results and calculational methods for long-wavelength spin waves in thin films and multilayers. While the primary attention is on ferromagnet-based structures, long-wavelength spin waves in antiferromagnets are also discussed. We indicate how particular measurements of spin wave frequencies can be used to extract the fundamental parameters of the different structures.