摘要:

We have observed an unexpected increase in the transmission of 24 GHz microwave power through thin pure, nickel slabs at liquid helium temperatures, and at an applied static magnetic field value corresponding to ferromagnetic resonance (FMR). This increase in power at FMR was particularly unexpected because our specimens were very thick compared with the anomalous skin depth at FMR, d/&dgr;∼100 to 1000. The nickel crystals were prepared from a boule having a residual resistance ratio in excess of 2000. The transmission amplitude ratio was found to be ca. 10−6for a specimen 8.2 &mgr;m thick, and having the static field oriented along the hard axis (100). The transmission ratio was approximately six times smaller when the static field was oriented along the easy axis (111). The anomalous transmission amplitude decreased rapidly with increasing temperatures, and was no longer observable at 25 °K in a specimen 8.2 &mgr;m thick. Numerical calculations using a non‐local conductivity and the assumption of specular scattering of the current carries at the specimen surfaces did not show any field dependence of the transmission at FMR. The origin of this effect is unknown, but is clearly related to the large mean free path at low temperatures (l∼d), since it was not observed in polycrystalline specimens having a residual resistance ratio ∼16.

ISSN:0021-8979    

DOI:10.1063/1.326977

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

According to conventional theories of microwave transmission through ferromagnetic metals the transmission of 24 GHz radiation through nickel slabs 5–10 &mgr;m thick should be unobservable. Nevertheless, experiments at room temperature have revealed a peak in the transmission of 24 GHz microwaves at FMR using nickel single crystals and annealed polycrystalline foils ca. 8 &mgr;m thick. It is proposed that this anomalous energy transport across the specimens at FMR is due to the phonon mode which is generated by magneto‐elastic coupling to the resonantly precessing magnetization. The calculations indicate that exchange plays a significant role in determining the intensity and the lineshape of the transmitted signal at FMR.

ISSN:0021-8979    

DOI:10.1063/1.326978

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The anomalous transmission of the electromagnetic energy through thick ferromagnetic films has been discovered. The effect is observed when the static magnetic field is either parallel or perpendicular to the sample surface and perpendicular to the r.f. field. In order to explain the new effect, the spectrum and the attenuation of coupled sound‐spin waves was calculated. The attenuation of the sound‐like waves is rather small and thus sound waves can carry electromagnetic energy through the sample.

ISSN:0021-8979    

DOI:10.1063/1.326979

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Coupling of propagating magnetostatic waves with resonant exchange dominated spin wave modes produces attenuation notches in the magnetostatic wave transmission response. The exchange resonances occur when kex=n&pgr;/d, where kexis the exchange wave number normal to the film plane, n is the mode number and d is the thickness of the epitaxial YIG film. Measurements of attenuation notch depth and position have been performed on as grown LPE‐YIG films and on films whose surface spins were pinned by ion milling, SiO2deposition or annealing. Coupling was strongest for magnetostatic volume waves with the magnetic bias field normal to the film. Coupling to magnetostatic surface waves was less strong and in accordance with theory magnetostatic volume waves propagating parallel to the magnetic bias field showed zero coupling. The various treatments increased the depth of the attenuation notches and produced a mode pattern consistent with spin pinning asymmetric between the two film surfaces. The probable source of coupling between the propagating magnetostatic waves and resonant exchange modes in as grown films are magnetic non‐uniformities in the YIG films due to transient layer or melt depletion effects.

ISSN:0021-8979    

DOI:10.1063/1.326980

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The optical and magneto‐optical constants of several magnetically soft thin film alloys have been determined for &lgr;=6328A˚ using the transverse Kerr effect and ellipsometric techniques. The coercive force and magnetization were also measured. The alloy systems Fe1−xBx(0.15?x?0.5) and Fe1−xSix(0.1?x?0.3) and iron‐overcoated permalloys were studied as were Fe, Co and permalloy for reference. When used as transverse Kerr effect mirrors for ring laser gyros, the Fe‐rich Fe‐Si alloys and iron‐overcoated permalloys have the best calculated performance.

ISSN:0021-8979    

DOI:10.1063/1.326981

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The present paper reports a theory for the excitation of magnetostatic forward volume waves (MSFVW’s) in YIG films by the most basic of all transducers, viz., an electric line current source, and various ramifications thereof (microstrip, meander‐line and grating couplers). Expressions for power in the MSFVW’s excited by these transducers are derived, and computations of the transducer excitation characteristics are presented. It is found that all transducers yield a significant excitation of higher‐order MSFVW’s, with the best suppression of these modes provided by the single microstrip coupler.

ISSN:0021-8979    

DOI:10.1063/1.326982

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

This paper reports results of theoretical and experimental studies of microwave delay line filters based on magnetostatic wave (MSW) propagation in epitaxial yttrium iron garnet (YIG) with multielement transducer pairs for wave launching and receiving. Filter transmission and input impedance characteristics for both magnetostatic surface wave (MSSW) and magnetostatic forward volume wave (MSFVW) devices have been calculated and measured experimentally. A planar, multilayer metal‐dielectric‐YIG geometry, permitting consideration of decoupling due to spacing between the transducers and YIG surface, is used to model the transducer. A ’’low’’ loss microstrip transmission line model is used to derive an equivalent transducer circuit. For assumed noninteraction of transducer element currents, the Poynting vector is used to determine the radiation resistance and the radiation reactance is derived from the Hilbert transform of this resistance. Experimental swept frequency measurements of insertion loss and input impedance versus frequency at S band have yielded experimental results which show good agreement with theoretical predictions of the model for a number of different configurations.

ISSN:0021-8979    

DOI:10.1063/1.326983

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Magnetostatic surface wave transducer theory is extended to include apodization and variable coupling. Results are presented for three types of apodization: conducting strip length, width weighting, and variable periodicity. An independent strip and a truncated array model are included. The dependence of radiation resistance on liftoff is exponential when there are no ground planes.

ISSN:0021-8979    

DOI:10.1063/1.326984

出版商:AIP    

年代:1979

数据来源: AIP