Fabrication and Magnetic Properties of Fe65Co35–ZnO Nano-Granular Films

A series of nano-granular films composed of magnetic metal (Fe65Co35) granules with a few nanometers in size and semiconductor oxide (ZnO) have been fabricated by a magnetron sputtering method, and excellent soft magnetic properties have been achieved in a wide metal volume fraction (x) range for as-deposited samples due to the exchange coupling between FeCo granules (a ferromagnetic interaction in nano-scale). In a wide range (0.53 <x < 0.71), the films exhibit coercivity HC not exceeding 15 Oe, along with high resistivity. Especially for the sample with x = 0.67, coercivities in hard and easy axes are 1.43 and 7.08 Oe, respectively, 4πMS = 9.85 kg, and ρ reaches 2.06 × 103 μΩ cm. The dependence of complex permeability μ = μ′ − jμ″ on frequency shows that the real part μ′ is more than 100 below 1.83 GHz and that the ferromagnetic resonance frequency reaches 2.31 GHz, implying the promising for high frequency application. The measured negative temperature coefficient of resistivity reveals that may be the weak localized electrons existing in samples mediate the exchange coupling

Perméabilité intrinsèque et extrinsèque de couches minces ferromagnétiques et de multicouches ferromagnétique-isolant en fonction de la fréquence : comparaison expérience - modèle

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Propriétés dynamiques d'alliages ferromagnétiques cobalt/métal de transition, faiblement substitués en terres rares magnétiques

Using radio-frequency (r-f) sputtering, we have prepared in presence of a static magnetic field, ferromagnetic thin films of composition (Co93Zr7)100 - yREy (RE = Nd, Pr, Dy, Tb... a magnetic rare earth element). The study was performed for small amounts of RE substitution (0 < y < 3). These films exhibit attractive soft magnetic properties similar to CoZr alloys : low coercivity (Hc ~ 1 Oe), and a high saturation induction (Bs 10 kG). A low in-plane uniaxial anisotropy Hk forms, whose magnitude depends upon the composition and the preparation parameters. Substitution by RE atoms affects essentially the µ frequency-response. Depending on the nature, the concentration of RE atoms and on the value of Hk, a high relative rotational permeability µ (µ' ~ 500-3000 at frequencies up to 500 MHz) was obtained. Also depending on RE and on y, high µ" (µ" ~ 400-3000 at ν ~ 1 GHz) distributed over a very broad frequency range (Ɗν ~ 500-2500 MHz) was measured. Using the Landau-Lifshitz equations for high frequency permeability and the values of the magnetic parameters measured by FMR, experimental spectra could be well approximated

Behavior of a common source traveling wave amplifier versus temperature in SOI technology

In this paper, the design and the results of a CMOS Silicon-on-Insulator (SOI) traveling wave amplifier (TWA) versus temperature are presented. The four stage TWA is designed with a single common source n-MOSFET in each stage using a 130 nm SOI CMOS technology requiring a chip area of 0.75 mm2 . A gain of 4.5 dB and a unitygain bandwidth of 30 GHz are measured at 1.4 V supply voltage for a power consumption of 66 mW. The designed circuit has been characterized over a temperature range from 25 to 300°C. The performance degradation on the gain of the TWA, the SOI transistors as well as the microstrip lines used for the matching network are analyzed. Index terms – SOI, Traveling Wave Amplifier, High temperature effect, Microstrip lines, DTMOS

An investigation of high temperature effects on CPW and MSL on SOI substrate for RF applications

One of the main markets for Silicon-onInsulator (SOI) devices is the high-temperature applications. In the last decade, the technology advances to deep submicron to improve device performances in term of cut-off frequency. Practical application of integrated circuits requires the consideration of a wide temperature range, and transmission lines are widely used in MMIC's as interconnects and matching networks. Therefore, there is a need to investigate the performances of the transmission line structures on SOI substrate in a wide temperature range, as a function of frequency. The behaviour of 50 Ω microstrip (MSL) and coplanar waveguide (CPW) transmission line topologies versus temperature is presented

Behaviour of TFMS and CPW line on SOI substrate versus high temperature for RF applications

Practical application of integrated circuits requires operation over a wide temperature range. In the case of microwave monolithic integrated circuits (MMICs), the quality of the interconnections as well as the passive matching networks in term of losses is predominent. Therefore, there is a need to investigate the performances of transmission line structures on Si-based substrates in a wide temperature range, as a function of frequency. The behaviour of 50 Ω thin film microstrip (TFMS) and coplanar waveguide (CPW) transmission line topologies on both standard and high resistivity silicon-on-insulator (SOI) substrates versus high temperature is presented