Transmission of microwaves through exchange-coupled bi-layer magnetic films in ferromagnetic and standing spin wave resonances

Journal of Applied Physics

2016

Self Cite

Abstract. We constructed a quasi-analytical self-consistent model of the striplinebased broadband ferromagnetic resonance (FMR) measurements of ferromagnetic films. Exchange-free description of magnetization dynamics in the films allowed us to obtain simple analytical expressions. They enable quick and efficient numerical simulations of the dynamics. With this model we studied the contribution of radiation losses to the ferromagnetic resonance linewidth, as measured with the stripline FMR. We found that for films with large conductivity of metals the radiation losses are significantly smaller than for magneto-insulating films. Excitation of microwave eddy currents in these materials contributes to the total microwave impedance of the system. This leads to impedance mismatch with the film environment resulting in decoupling of the film from the environment and, ultimately, to smaller radiation losses. We also show that the radiation losses drop with an increase in the stripline width and when the sample is lifted up from the stripline surface. Hence, in order to eliminate this measurement artefact one needs to use wide striplines and introduce a spacer between the film and the sample surface. The radiation losses contribution is larger for thicker films.

“…Substitution of Eqs. (13,14) into Eq. (16) allows one to eliminate the unknown integration constant B…”

Section: Numerical Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Coupling of microwave magnetic dynamics in thin ferromagnetic films to stripline transducers in the geometry of the broadband stripline ferromagnetic resonance

Journal of Applied Physics

2016

Self Cite

“…Unfortunately, this study was carried out for partial pressures well above 1 atmosphere (1.3-5.2 atm). The works [28,29] reported a decrease in PMA on hydrogen absorption. Methods which are very impractical for sensor applicationsvibrating sample magnetometry and polarized neutron reflectivity -were utilized in these works.…”

mentioning

confidence: 99%

“…An extremely low amplitude microwave field can penetrate an electrically insulating wall and probe the sensor through the wall. More importantly, because the sensor is made from metallic conductors, the sensor itself serves as a perfect shield for microwaves [27][28], not allowing the microwave power to penetrate into the vessel that potentially contains the hydrogen gas. Thus, there will be no electrical fields capable ignite the gas present inside the vessel.…”

mentioning

confidence: 99%

Metallic spintronic thin film as a hydrogen sensor

Chang

Applied Physics Letters

Ivanov

2013

We investigate the response of palladium-cobalt bi-layer thin films to hydrogen charging at atmospheric pressure for spintronic applications. We find that hydrogen absorption by the palladium layer results in the narrowing and shifting of the ferromagnetic resonance line for the material. We explain the observed phenomena as originating from reduction in spin pumping effect and from variation in the magnetic anisotropy of the cobalt film through an interface effect. The shift of the resonance frequency or field is the easiest to detect. We utilize it to demonstrate functionality of the bi-layer films as a hydrogen sensor.Recently, the demand for highly stable and sensitive hydrogen gas sensors has increased due to growing importance of fuel cell applications. Various types of hydrogen gas sensors have been proposed [1]. All the proposed sensors have a number of drawbacks. In particular, sensors either based on variation of resistance of semiconductors [2], or on catalytic oxidation of noble metals * Corresponding author.

“…It takes a couple of more seconds to convert the obtained Z r values into S21 by using Eqs. (18)(19)(20)(21)(22)(23)(24)(25) from [16].…”

Section: Theorymentioning

confidence: 99%

Theoretical Study of the Stripline Ferromagnetic Resonance Response of Metallic Ferromagnetic Films Based on an Analytical Model

Hai

2016

SPIN

Self Cite

Abstract:We develop an advanced analytical model for calculating the broadband stripline ferromagnetic resonance (FMR) response for metallic ferromagnetic films, taking into account the exchange interaction as well as the exchange boundary conditions at the film surface. This approach leads to simple analytical expressions in the Fourier space. As a result, a numerical code which implements inverse Fourier transform of these equations is very quick. This allows us to explore a wide space of parameters as numerical examples of application of this theory. In particular, we investigate the joint effect of microwave eddy current shielding and magnetisation pinning at the ferromagnetic film surfaces on the shape of the stripline FMR response of the film.