High attenuation tunable microwave notch filters utilizing ferromagnetic resonance

Abstract

We have constructed a series of microstrips for transmission of microwaves. These microstrips incorporate ferromagnetic and dielectric layers and therefore absorb microwave energy at the ferromagnetic resonance (FMR) frequency. The absorption notch in transmission can be tuned to various frequencies by varying an external applied magnetic field. For our devices, which incorporate Fe as the ferromagnetic material, the resultant FMR frequencies range from 10–20 GHz for applied fields up to only 1000 Oe. This frequency range is substantially higher than those found in devices utilizing a dielectric ferrimagnet such as YIG. We constructed devices using monocrystalline Fe films grown in a molecular beam epitaxy system. Our devices are of different construction than other Fe dielectric microstrips and show much improvement in terms of notch width and depth. We observed maximum attenuation on the order of 100 dB/cm, much larger than previously reported values of 4 dB/cm.

10 GHz bandstop microstrip filter using excitation of magnetostatic surface wave in a patterned Ni78Fe22 ferromagnetic film

“…The low-frequency peak of attenuation constant versus frequency can be associated with FMR of a ferromagnetic core. [1][2][3][4][5][6][7][8] The observed frequency shift with respect to the expected thin-film FMR frequency ͑2.4 GHz͒ is partly due to the combination of a high magnetic damping constant and a small width of a signal line, 9 as well as the influence of a high-frequency component ͑peak HF͒. For sample B, the attenuation constant versus frequency demonstrates no low-frequency FMR component but only a high-frequency contribution close to 10 GHz ͓Fig.…”

“…[1][2][3][4][5][6] In particular, it was demonstrated for a microstrip with yttrium iron garnet magnetic core, saturated perpendicular to the plane of the strip line, that transmission characteristics of the line show strong coupling phenomena between quasi-TEM and magnetostatic surface wave ͑MSSW͒ modes. 2 On the other hand, for a microstrip with a tangentially ͑in-plane͒ magnetized magnetic core, the effect of the MSSW mode has been ignored; even the possible tracks of these modes can be seen from experimental data.…”

Tunable metamaterial bandstop filter based on ferromagnetic resonance

“…16,17 FMR-based bandstop filters rely on resonance to absorb microwave power at the FMR frequency. 18 By interacting with an incoming microwave, FMR can arise in ferrite under an applied magnetic field. [19][20][21] The FMR frequency can be influenced by the applied magnetic field, the property of used ferrite and the composite structure of the metamaterial.…”

The effect of a neighboring metal layer on the high-frequency characteristics of a thin magnetic stripe

“…[1][2][3][4][5][6][7] Such studies are particularly important in view of the potential application of FM elements in magnetic data storage and microwave devices. [8][9][10][11] In many cases, however, magnetic elements do not stand alone, but are ͑par-tially͒ surrounded by metallic conductors. One, for instance, can think of microwave transmission lines with FM cores [9][10][11] or inductive techniques utilizing coplanar waveguides for probing magnetization dynamics in thin films.…”

“…[8][9][10][11] In many cases, however, magnetic elements do not stand alone, but are ͑par-tially͒ surrounded by metallic conductors. One, for instance, can think of microwave transmission lines with FM cores [9][10][11] or inductive techniques utilizing coplanar waveguides for probing magnetization dynamics in thin films. 12,13 Nevertheless, the effect of neighboring metallic layers on the spinwave spectra of confined magnetic samples has not been investigated, although the former's influence on the dispersion relation of spin waves in infinite films is well known.…”