Spin Waves In Yttrium Iron Garnet Research Articles

Spin wave propagation in ultrathin magnetic insulators with perpendicular magnetic anisotropy

Magnetic thin films with perpendicular magnetic anisotropy (PMA) offer opportunities for studying magnetostatic forward volume mode (MSFVM) spin waves with isotropic propagation. Here, we realize the full reciprocal MSFVM spin wave propagation in a 30-nm-thick manganese doped yttrium iron garnet (YIG) with PMA by only applying an external field of 5 mT. The external magnetic field required for investigating the MSFVM spin waves in YIG is reduced by 34 times compared to the in-plane magnetized one. The spin wave group velocity and decay length are also investigated. Our finding paves the way for applications of isotropic magnonic computing systems and logic devices.

Resonant excitation of spin waves in hybrid nanostructures via frequency combs

Here we propose a new method of resonant optical excitation of spin waves in hybrid nanostructures via frequency comb. We consider a two-layer nanostructure consisting of an Au layer with a grating on the top and an yttrium iron garnet (YIG) thin film at the bottom. The plasmon evanescent fields induce time-independent magnetic polarization via the transverse magneto-optical Kerr effect (TMOKE) at the Au-YIG interface. Thus magnetic polarization in turn plays a role of a source for the excitation of the spin waves in YIG film. We show that by using the frequency comb as a source we can generate the magnetic polarization in resonance with the spin waves in YIG thus substantially increasing the magneto-optical response of the system. These results open new routes in the optical control of spintronics systems.

Exchange-torque-induced excitation of perpendicular standing spin waves in nanometer-thick YIG films

Spin waves in ferrimagnetic yttrium iron garnet (YIG) films with ultralow magnetic damping are relevant for magnon-based spintronics and low-power wave-like computing. The excitation frequency of spin waves in YIG is rather low in weak external magnetic fields because of its small saturation magnetization, which limits the potential of YIG films for high-frequency applications. Here, we demonstrate how exchange-coupling to a CoFeB film enables efficient excitation of high-frequency perpendicular standing spin waves (PSSWs) in nanometer-thick (80 nm and 295 nm) YIG films using uniform microwave magnetic fields. In the 295-nm-thick YIG film, we measure intense PSSW modes up to 10th order. Strong hybridization between the PSSW modes and the ferromagnetic resonance mode of CoFeB leads to characteristic anti-crossing behavior in broadband spin-wave spectra. We explain the excitation of PSSWs by exchange coupling between forced magnetization precessions in the YIG and CoFeB layers. If the amplitudes of these precessions are different, a dynamic exchange torque is generated, causing the emission of spin waves from the interface. PSSWs form when the wave vector of the spin waves matches a perpendicular confinement condition. PSSWs are not excited if exchange coupling between YIG and CoFeB is eliminated by a 10 nm Ta spacer layer. Micromagnetic simulations confirm the exchange-torque-driven mechanism.

Modulation of the Spectral Characteristics of a Nano-Contact Spin-Torque Oscillator via Spin Waves in an Adjacent Yttrium-Iron Garnet Film

NiFe-Cu-Co trilayer nano-contact spin-torque oscillators (NC-STOs) fabricated on an yttrium-iron garnet (YIG) film were studied in two different modes. In passive mode, i.e. without any NC-STO auto-oscillations, a microwave current through the nano-contact can excite spin waves (SW) in the YIG film, and, vice versa, antenna generated SWs in the YIG film can be detected by the nano-contact. In active mode, i.e., in the presence of auto-oscillations, significant changes appear in the NC-STO spectrum when its frequency approaches that of the SWs excited in the YIG. These results demonstrate strong coupling between NC-STOs and SWs in YIG and open new possibilities of 1) pure spin-current generation in YIG by NC-STOs; 2) mutual locking of a number of NC-STOs through SWs in YIG; and 3) improvement of NC-STO spectra through SW feedback in YIG.

Spin wave excitation in yttrium iron garnet films with micron-sized antennas

In this paper, we explore spin waves excitation in monolithic structures based on yttrium iron garnet (YIG) films with micro-sized antennas. Samples based on plain and patterned YIG film were fabricated and tested for tangential bias field geometries. We observed spin wave excitation and propagation with wave numbers up to 3.5 × 104 rad/cm. The corresponding wavelength is thus shorter more than by one order of magnitude compared to previous experiments with such films. For the sample with a periodic array of nanotrenches, we observed the effect of the shape anisotropy resulting in the shift of the spin wave propagation band in comparison to the unpatterned YIG film. Our results are very promising for the exploitation of short spin waves in YIG and provide great opportunity for significant miniaturization of YIG film based microwave devices.

Parametric chaos in yttrium-iron garnet films grown from weakly dissociated solution melt

We present the results of a comparative study of the chaotic generation of parametric spin waves in yttrium-iron garnet (YIG) films grown from a standard solution melt and in the films grown from a weakly dissociated solution melt containing garnet ferrite and orthoferrite clusters. It is shown that the efficiency of magnetic chaos generation is significantly higher in the latter case.

Scattering of Polarized Neutrons by Spin Waves in YIG

The neutron diffraction technique has been employed to study the inelastic scattering of polarized 1.08-Å neutrons by magnetic spin waves in yttrium iron garnet (YIG) at room temperature. Measurements were made for the case when the YIG scatterer was oriented near the position for (220) Bragg reflection. Quantitative confirmation has been obtained for the theoretical predictions of the dependence of this scattering on the incident neutron polarization. Two new methods are described for determining the parameter D appearing in the expression Dk2 for the energies of long-wavelength acoustic magnons in usual ferromagnets and ferrimagnets. These methods require only measurements of the peak intensities of the diffuse magnetic reflections. The values D=0.25(+0.04, −0.03) eV·Å2 and D=0.26±0.02 eV·Å2 have been obtained for YIG by these procedures.