dc Effects in Ferromagnetic Resonance in Thin Ferrite Films

Heinz, W.W.; Silber, L.

doi:10.1063/1.1728705

Cited by 4 publications

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“…Despite these difficulties there was a small amount of early work performed using high power pulsed microwaves following either Juretschke's waveguide technique [172] or an analogous approach with microwave cavities [173] (which allowed mV voltages at slightly lower power). This very early work is briefly summarized in Ref.…”

Section: Ferromagnetic Films: Early Studies Using Pulsed Microwave Somentioning

confidence: 99%

Electrical detection of magnetization dynamics via spin rectification effects

2016

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The purpose of this article is to review the current status of a frontier in dynamic spintronics and contemporary magnetism, in which much progress has been made in the past decade, based on the creation of a variety of micro-and nano-structured devices that enable electrical detection of magnetization dynamics. The primary focus is on the physics of spin rectification effects, which are well suited for studying magnetization dynamics and spin transport in a variety of magnetic materials and spintronic devices. Intended to be intelligible to a broad audience, the paper begins with a pedagogical introduction, comparing the methods of electrical detection of charge and spin dynamics in semiconductors and magnetic materials respectively. After that it provides a comprehensive account of the theoretical study of both the angular dependence and line shape of electrically detected ferromagnetic resonance (FMR), which is summarized in a handbook formate easy to be used for analyzing experimental data. We then review and examine the similarity and differences of various spin rectification effects found in ferromagnetic films, magnetic bilayers and magnetic tunnel junctions, including a discussion of how to properly distinguish spin rectification from the spin pumping/inverse spin Hall effect generated voltage. After this we review the broad applications of rectification effects for studying spin waves, nonlinear dynamics, domain wall dynamics, spin current, and microwave imaging. We also discuss spin rectification in ferromagnetic semiconductors. The paper concludes with both historical and future perspectives, by summarizing and comparing three generations of FMR spectroscopy which have been developed for studying magnetization dynamics.

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Section: Ferromagnetic Films: Early Studies Using Pulsed Microwave Somentioning

confidence: 99%

Electrical detection of magnetization dynamics via spin rectification effects

2016

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8. Ferromagnetische Resonanz

Frait

1962

Physica Status Solidi (b)

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dc Detection of Spin Resonance in Thin Metallic Films

Juretschke¹

1963

Journal of Applied Physics

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Ohm's law in strongly magnetic, though not necessarily ferromagnetic materials, has leading terms in the presence of a magnetization M and an induction B of the form E=ρJ−R0J×B−R1J×M+Δρ/M2(J·M)M+…,which represent the ordinary and extraordinary Hall effects and a magnetoresistance. The M-dependent terms, in particular, describe interactions due to polarized scattering centers and to the left-right asymmetry of polarized mobile charge carriers.1 An electromagnetic wave interacting with such a material will, under resonance conditions, cause a precession of M, while at the same time inducing an eddy current density J. According to Eq. (1), the presence of two such terms at microwave frequencies introduces local dc electric fields related to the time average of the various products. These fields will be largest near spin resonance. Such fields are observable only in films thin compared to the electromagnetic skin depth,2 and they may be used either to study spin resonance in very thin films or to determine their transport properties at microwave frequencies. In particular, for a configuration in which the static field is in the film plane and the electromagnetic wave is at normal incidence 〈J×B〉 has no contribution in the film plane; such an experiment allows a separation of R0 and R1 even in materials which show no magnetic saturation. The detailed electromagnetic theory of this configuration has been worked out3 for an isotropic material and experiments have been carried out on nickel films to test the various features of the theory, and to determine the usefulness of the method in studying high-frequency magnetic and conduction properties in thin films.4 The experimental arrangement consists of placing the sample close to a wave guide or cavity wall, but insulated from it, and measuring the dc voltages, either steady or modulated, induced by the microwaves. The major precaution necessary for a quantitative study is that the microwave field pattern within the film must be well known, so that sample geometry, its electrical boundary conditions, and placement of detection wires is very critical. The experimental results reproduce all the qualitative features of the theory, with regard to sample thickness, local field configuration, power, and magnetic field orientation. The agreement with the theory is better than reported by Seavey5 for Permalloy films, most likely because of differences in local field configuration, and by Heinz and Silber6 for a ferrite, whose experiment did not permit separation of all parameters. A quantitative analysis of the data7 gives consistent values of the magnetic resonance parameters g, M0, and τ. It also requires that the films be described at microwave frequencies by a complex conductivity which is generally smaller than at low frequencies. Within the over-all accuracy of the analysis—about 15%—the magnetoresistance Δρ is the same as at low frequencies, and the increase of R1 is related to that of ρ, so that no dispersion of these constants is observed. The same method has been applied to thin films of gadolinium, and while the signals are much smaller, the dc effects clearly persist in the paramagnetic region above room temperature.8 Quantitative analysis of the data has been impeded because the power levels necessary to observe the signals cause considerable heating of the sample. Since both the magnetic and galvanomagnetic properties of gadolinium are very temperature sensitive, a careful determination of the local temperature within the film during the microsecond long pulse of microwaves is required. The data obtained so far indicate that the g value of our gadolinium films is higher than in bulk, and that the extraordinary Hall constant appears to be larger than in bulk material.

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dc Effects in Ferromagnetic Resonance in Thin Ferrite Films

Abstract: The dc voltage which accompanies ferromagnetic resonance has been observed in thin films of magnetite. The dependence of this voltage on microwave power and static magnetic field is in qualitative agreement with theory, but larger by a factor of 3.

Cited by 4 publications

References 2 publications

Electrical detection of magnetization dynamics via spin rectification effects

Electrical detection of magnetization dynamics via spin rectification effects

8. Ferromagnetische Resonanz

dc Detection of Spin Resonance in Thin Metallic Films

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