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In-plane angular ( H ) variation of acoustic resonance field (H res ) at room temperature experimental; and theoretical;— for antiferromagnetically coupled Fe8 nm/Si1.0 nm/Fe10 nm trilayer film studied by FMR at 24 GHz. The insets show the Fe magnetization directions at different resonance field values.
Source publication
Strong antiferromagnetic interlayer exchange coupling across an insulating spacer is in increasing demand for high-density magnetic recording. We report here on the interlayer exchange coupling of epitaxial Fe(8 nm)/Si(t)/Fe(10 nm) trilayers as a function of Si thickness studied by ferromagnetic resonance FMR, Brillouin light scattering, and magnet...
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This report deals with the interlayer exchange coupling of epitaxial Fe(3 nm)/Al(tAl=0.4–0.9 nm)/Fe(2 nm) trilayers studied by using ferromagnetic resonance (FMR), Brillouin light scattering (BLS) and magneto-optic Kerr effect (MOKE) measurement techniques. A very strong antiferromagnetic (AFM) interlayer exchange coupling (≫3 erg/cm2) was observed...
Citations
... Layered structures which are known to have simultaneous BL and BQ IEC are Fe/Si multilayers (MLS), in which both couplings can be widely changed by tuning the Si spacer-layer thickness, and which were studied using different methods [27][28][29][30][31][32][33][34]. Many interesting magnetic behaviors in Fe/Si structures have been observed and were related to the spontaneously formed iron silicide layers of different structure and composition at the interfaces [33][34][35]. ...
Important aspects of exchange-coupled magnetic layered structures are related to the noncollinear arrangement of sublayer magnetizations which can arise from competition between bilinear (BL) and biquadratic (BQ) interlayer exchange coupling (IEC). In this work, the influence of coexisting BL and BQ IEC of different strengths on magnetization precession in layered systems is investigated both experimentally and theoretically. Laser-induced magnetization precession has been studied in the Fe/Si(dSi) multilayers (MLS) as a function of the amplitude (H) and orientation angle (θH) of external magnetic field using time-resolved magneto-optical Kerr (TRMOKE) effect. Strongly changing characters of precession frequency dependencies ω(H,θH) for Fe sublayer thickness dFe=3 nm and Si spacer-layer thicknesses (dSi) varying in the range of 0.9–2.4 nm have been observed. Analytical formulas for acoustic and optic mode dispersion relations with coexisting BL and BQ IEC, scaled by J1 and J2 parameters, respectively, for the in-plane effective magnetic anisotropy and arbitrary magnetic field direction were derived, and very good agreement with the experimentally observed frequency dependencies has been obtained. It is shown that BQ coexisting with BL IEC significantly influences on the magnitude and form of dispersion relations. From analytical formula derived, it follows that zero-field optical mode frequency tends to zero as |J1| approaches 2J2. The acoustic and optic mode-crossing effect has been observed and it is found that values of crossing fields and frequency gaps strongly increase as θH angles decrease and depend on relative BL and BQ IEC strengths. The BL IEC is of ferromagnetic type with J1≈1.6 mJ/m2 for the MLS with dSi=0.9 nm, and changes to antiferromagnetic one with J1≈−0.9 mJ/m2 for the MLS with dSi=1.4 nm, while the J2 parameter of BQ IEC decreases from 1.8 to 1.0 mJ/m2. The coupling strengths decrease by one to two orders of magnitude for the sample with dSi=2.4 nm, but both mode frequencies are still observed and well reproduced by the theory. It is shown that J1 and J2 parameters obtained in the TRMOKE experiment coincide within the estimated error bars with the determined from independent measurements of magnetization processes in the static magneto-optical Kerr effect and interpreted with the use of analytical formulas derived. Numerical solutions of coupled Landau-Lifshitz-Gilbert (LLG) equations for acoustic and optic modes, with inclusion of BL IEC, intrinsic Gilbert damping, and spin-pumping damping terms, and extended to include BQ IEC, were performed and fitted to experimental data. It is shown that determined effective damping coefficients on H and θH dependencies for acoustic and optic modes are very well simulated with the use of LLG equation solutions with Gilbert damping, spin-pumping-damping–related effective spin-mixing conductance, and spin-diffusion length parameters included. The dependencies of the parameters on dSi spacer-layer thickness are discussed and compared with available data for other systems.
... The increasing demand for higher frequency magnetic microwave structures triggered a tremendous development in the field of magnetization dynamics over the past decade. In order to develop smaller and faster devices, a better understanding of the complex magnetization precessional dynamics, the magnetization anisotropy, and the sources of spin scattering at the nanoscale is necessary232425. Magnetic data storage with its promise of non-volatility, robustness, high speed and low energy dissipation attracted long back. ...
Ferromagnetic resonance (FMR) is a very powerful experimental technique in the study of ferromagnetic nanomaterials. The precessional motion of a magnetization M of ferromagnetic material about the applied external magnetic field H is known as the Ferromagnetic resonance (FMR). In the physical process of resonance, the energy is absorbed from rf transverse magnetic field hrf, which occurred when frequency matched with precessional frequency (ω). The precession frequency depends on the orientation of the material and the strength of the magnetic field. It allows us to measure all the most important parameters of the material: Curie temperature, total magnetic moment, relaxation mechanism, elementary excitations and others.
Part of the classical approach to ferromagnetism is to replace the spins by a classical micro-spin vector M magnetization. The time-dependence of the magnetization can be obtained directly by calculating the torque acting on M by an effective field Heff,
In the frequency domain measurements, the magnetic excitation is sinusoidal magnetic field hrf and the response of the sample is detected by vector network analyzer. The magnetic field can be applied along parallel and perpendicular direction of the nanowires satisfying the FMR condition. The main components of the experimental setup are shown in Fig. 13. The VNA is connected to a coplanar waveguide (CPW) having a characteristic impedance of 50 Ω using coaxial cables and microwave connectors. For such radio frequency connections often coaxial cables with Teflon insulation and SMA connectors are employed. They are comparably low priced and offer a bandwidth of typically 18 GHz. The used cables should not have a metallic reinforcement.
The book Ferromagnetic Resonance - Theory and Applications highlights recent advances at the interface between the science and technology of nanostructures (bilayer-multilayers, nanowires, spinel type nanoparticles, photonic crystal, etc.). The electromagnetic resonance techniques have become a central field of modern scientific and technical activity. The modern technical applications of ferromagnetic resonance are in spintronics, electronics, space navigation, remote-control equipment, radio engineering, electronic computers, maritime, electrical engineering, instrument-making and geophysical methods of prospecting.
http://www.intechopen.com/books/ferromagnetic-resonance-theory-and-applications
