Selective excitation of magnetostatic modes of a thin film

A ferromagnetic resonance technique for selective excitation of various series of magnetostatic modes of a thin film is presented. Microwave absorption spectra of a YIG film are recorded in various configurations. The observed resonance fields for both surface and volume modes are found to be in good agreement with the fields calculated from a generalized form of the Damon-Eshbach formula.     

Evidence of unpinned magnetostatic modes in a thick yttrium-iron-garnet epilayer

It is shown that the frequencies of the ferromagnetic normal modes of a thick (70 μm) yttrium-iron-garnet epilayer are in agreement with Sparks' equations for the unpinned main magnetostatic branch. The exchange term is found to be negligible.     

Radiation damping of magnetostatic modes in yig

The radiation induced linewidth of magnetostatic modes in spheres of Yttrium Iron Garnet has been measured in microwave experiments. The linewidths of the lowest order modes (n m 0) have a ω²ⁿ⁺¹ frequency dependence which can be explained by multipole radiation.     

Bulk and surface magnetostatic modes in superlattices

General dispersion equations for the magnetostatic modes in infinite and semi-infinite superlattices are derived by the transfer matrix method for the case of superlattices with an elementary unit consisting of N (N arbitrary) ferromagnetic layers. The films are assumed to be magnetized parallel to the film surfaces and parallel to an external magnetic field. Explicit forms of the dispersion equations, together with exemplary dispersion curves of surface modes and bands of bulk waves, are given in the case of N = 2.     

Electrostatic and magnetostatic modes in semiconductor superlattices

We present a study of interface optical phonons and magnetostatic modes in semiconductor superlattices. We first review the propagation of longitudinal waves propagating parallel to the superlattice axis in order to show the similarities and differences between these and the interface modes just mentioned. The interface modes are discussed with the aim to interpret experiments carried out with superlattices of diluted magnetic semiconductors.     

The magnetostatic modes in planar one-dimensional magnonic crystals with nanoscale sizes

The plane-wave method is used to determine the spin-wave spectra in nanoscale one-dimensional magnonic crystals formed by a periodic lattice of ferromagnetic stripes. The dynamic demagnetizing field in a new formulation is used in these calculations. The calculated spectra of spin waves are compared with experimental data taken from literature and a good agreement is obtained. The dependence of the spin-wave spectra on magnetic material parameters consisting of magnetic stripes is systematically studied. We proved that the experimentally found magnonic band structure with two magnonic gaps is of magnetostatic nature.     

Theory of magnetostatic waves in a ferrite film with transition layers

A dispersion relation is derived for magnetostatic waves in a ferrite film with inhomogeneous layers near the interfaces. It is shown that the transition layers can be taken into account using a single integrated parameter, namely, the effective film thickness. It is established that the layered structure of the film causes an extra wave damping. The relations obtained can be used to analyze the dispersion and damping of the main modes of magnetostatic waves.     

Observation and analysis of magnetostatic modes in K2CuF4

By means of ferromagnetic resonance experiments, we have observed magnetostatic modes in the quasi-two-dimensional transparent ferromagnet K₂CuF₄. In spite of the problems with the shape of the sample resulting from layer structure properties of K₂CuF₄, we have been able to analyse the magnetostatic modes in terms of a normally magnetised disk.     

Calculations of magnetostatic mode frequencies in a 70 μm-thick film of YIG

Some microwave measurements performed on a film of YIG and described recently in this journal by Borghese et al. have been examined. It is shown that, for the parallel-field case, quantitative agreement can be obtained between most of the observed lines and the results of calculations based on that theory of Damon and Eshbach. It is also suggested that, for such films of YIG, 4πM₀ is about 1800 G, which is significantly higher than for the bulk material.     

A granular high-temperature superconductive film in the field of a magnetostatic surface wave

The reflection of a magnetostatic surface wave from a strip of a granular high-temperature superconductor is investigated. An expression obtained by the method of perturbations describes the field of the scattered wave. The coefficient of reflection of the MSSW from the HTSC strip is calculated as a function of frequency and temperature. It is shown that the reflectance is very low at temperatures above critical and that the HTSC ceramic behaves as an ordinary superconductor. The reflectance rises sharply when the temperature drops below critical. As the critical current decreases, the reflectance drops off and the film loses the high-temperature properties. An expression is derived for the loss resistance of the MSSW in a granular HTSC film. The loss resistance amounts to a few kiloohms and falls off sharply as the film transitions to the superconductive state. The results can also be developed for periodic HTSC structures and used in the design of frequency-selective devices, as well as high-speed bolometric photodetectors. Tomsk State University of Control Systems and Electronics. Translated Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 97–102, July, 1998.     

Thermostabilization of magnetostatic wave frequency and group velocity in a cubic ferrite film

The conditions for thermostability of the group velocity and frequency of magnetostatic waves in a ferromagnetic layer were studied theoretically. The temperature dependence of the bias field parameters was determined from the conditions for simultaneous thermostability of the frequency and group velocity. Particular emphasis was placed on ferrite films with cubic anisotropy.     

Numerical simulation of quasisurface magnetostatic waves in a ferrite film with two magnetic channels

Quasisurface magnetostatic waves propagating in a ferrite film along two magnetized channels are simulated numerically. It is shown that the interaction between the channels is manifested differently, depending on the wavelength. In the long-wavelength region the interaction between the channels has a distributed character; in the short-wavelength region the interaction between the channels appears as if it takes place at their boundary. The magnetized region of the ferrite film between the channels behaves both as a conductor of the alternating field and as a medium with eigenmodes, so that under certain conditions the waveguide can be transformed into a three-channel structure. The dispersion curves of the magnetostatic wave modes of a two-channel waveguide lie in zones bounded by the dispersion curves of the corresponding modes of a one-channel waveguide of double width. As the gap between the channels increases, the dispersion curves of the odd modes shift toward shorter wavelengths, and those of the even modes shift toward longer wavelengths. Zh. Tekh. Fiz. 68, 91–96 (February 1998)     

The influence of radiation reaction damping on the ESR lineshape of non-Lorentzian lines and magnetostatic modes

In the quasi-two-dimensional ferromagnet (C₂H₅NH₃)₂CuCl₄ magnetostatic modes have been observed in the temperature rangeT=4.2...20 K by a shorted waveguide technique. The spectra differ significantly from recently reported ESR measurements in a cavity. The discrepancy can be explained by radiation damping effects which do not only broaden a line but can also essentially affect the lineshape. A simple experimental method is proposed to test the non-Lorentzian character of ESR lineshapes.     

Localization properties of bulk-dead and comb magnetostatic modes in Brillouin light scattering spectrum

We show that magnetostatic modes with amplitude localized in different regions of the sample along the direction of the magnetic field occur in ferromagnetic stripes: bulk-dead modes, with amplitude localized in two regions and comb modes localized in its central part. We also demonstrate these localization properties can be studied by Brillouin light scattering techniques and applied in practice. Having established that the localization of these modes varies with their frequency, we use this finding as the basis of a trial reinterpretation of experimental results obtained by Demidov et al. [Appl. Phys. Lett. 92 (2008) 232503].     

Al/CdSe/GaSe/C resonant tunneling thin film transistors

An Al/CdSe/GaSe/C thin film transistor device was prepared by the physical vapor deposition technique at a vacuum pressure of 10⁻⁵ mbar. The x-ray diffraction measurements demonstrated the polycrystalline nature of the surface of the device. The dc current-voltage characteristics recorded for the Al/CdSe/C and Al/CdSe/GaSe/C channels displayed a resonant tunneling diode features during the forward and reverse voltage biasing, respectively. In addition, the switching current ratio of the Al/CdSe/C increased from 18.6 to 9.62×10³ as a result of the GaSe deposition on the CdSe surface. Moreover, the alternating electrical signal analyses in the frequency range of 1.0 MHz to 1.8 GHz, showed some remarkable properties of negative resistance and negative capacitance spectra of the Al/CdSe/GaSe/C thin film transistors. Two distinct resonance-antiresonance phenomena in the resistance spectra and one in the capacitance spectra were observed at 0.53, 1.04 and 1.40 GHz for the Al/CdSe/C channel, respectively. The respective resonating peak positions of the resistance spectra shift to 0.38 and 0.95 GHz when GaSe is interfaced with CdSe. These features of the thin film transistors are promising for use in high quality microwave filtering circuits and also for use as ultrafast switches.     

The propagation of magnetostatic surface waves in ferrite/superconductor structures

An electrodynamic model that describes the dispersion of magnetostatic surface waves in ferrite/superconductor structures is suggested. On its basis, a new approach to determining the microwave sheet resistance R _S of superconducting films in a magnetic field is elaborated. The values calculated (R _S =0.20–0.96 mΩ) agree with results obtained by the Tauber method. For YIG/YBCO structures, the controllable phase shift is about 1.5π when the depth of magnetostatic wave penetration into the YBCO film varies from 2.0 to 0.8 μm.     

Parametric interaction of volume magnetostatic waves in a ferrite film with spatiotemporal modulation of the magnetic field

Effects of the resonant Bragg scattering of magnetostatic backward volume waves on the periodic structure of a conductive meander pattern with an alternating current are analyzed theoretically and compared with experiment. It is shown that unlike a static grating, a dynamic grating causes a frequency shift of the scattered wave. It is proposed that this phenomenon be utilized for effective control of the intermodal conversion of magnetostatic waves. Zh. Tekh. Fiz. 68, 105–112 (May 1998)