Research On Performance And Application Of RF Integrated Nano Soft Magnetic Thin Films

It is a major challenge for magnetic integrated device technology in the field of electron information, at present. And magnetic integrated device technology plays an important role in information storage, information detection, information transmission, information sensing, information identification and other practical applications. Nowadays, the application of magnetic thin films have included power supplies, inductors, transformers, sensors, impedance, electromagnetic noise suppressor, spin microwave source and GMR head. The micro electronic devices will produce high density, broadband electromagnetic signals when information exchange, data transmission, voltage current and then energy conversion occurs. It makes the electromagnetic environment complicated. So it is needed to resist electromagnetic interference technology in interdisciplinary research.The magnetic thin films applied to a micro magnetic electronic device must have the following properties, in order to meet the requirements of high working frequency, high integration and high transmission rate. Large resistivity, large magnetization and proper uniaxial planer anisotropy are needed to maintain in the film’s high-frequency characteristic. In this paper, we study the two magnetic systems of iron and cobalt films. It contains post annealing of nanocrystalline CoNbZr soft magnetic thin films by electric pulse and film noise suppressor projected with FeCo-YSZ nanocrystalline granular films. The contents are divided into four parts shown as follows.1. Electric pulse annealing system contains current generating section and test platform. It can output square wave, peak wave and triangle wave. It has adjustable duty cycle as well as current peak of 2.5 A. The test platform can also limit current flow by regulating the resistance. Moreover, the electric pulse output power can be adjusted in a wide range. An oscilloscope is used to observe the voltage of the sample and the pulse waveforms.2. It is the first time for soft magnetic thin films to be annealed using electric pulse. The microstructure and magnetic properties of the thin films were also studied. Because of the pulse current, the saturation magnetization of the films increases from 7.89 kGs to 12.67 kGs, and ferromagnetic resonance field decreased from 870 Oe to 764 Oe. The resonance frequency of the film is 2.3 GHz when the annealing electric pulse is 0.54 W. The saturation magnetization and the effective anisotropy field are improved as well. Because of the competition of the grain growth and nucleation, the grain size of the thin film is refined during annealing progress.3. It is the first application of ytttiun-doped zirconium(YSZ) to be added into FeCo alloy film. A high saturation magnetization, a low coercivity, a FMR frequency of 3.5 GHz, and a high resistivity were obtained. Magnetic grains are dispersed in non-magnetic YSZ. It is found that the YSZ can refine the grain and enhance the exchange coupling effect of the magnetic grains. Furthermore, by changing the process parameters, the high frequency magnetic properties of the thin films can be adjusted in a wide range. The properties 4πMs=21 kGs,cH =7.4 Oe, ? =589 μΩcm, rf =3.5 GHz are obtained. The microscopic mechanism and physical mechanism of magnetic properties are analyzed as well.4. We have designed thin film noise suppressor with FeCo-YSZ nanocrystalline granular films. When electromagnetic signal transmits through the CPW, the noise signal is absorbed by the thin film, S21=-8.3 dB, rf =3.8 GHz. We also studied the relationship between the film properties and its noise restraining ability. Although there are differences between compositions and thicknesses of the films, electromagnetic signals are rarely absorbed in low frequency range. It indicates that the low frequency effective signal can be smoothly passed through the thin film with little loss, and only the high-frequency noise signals are suppressed. It is proved that the FeCo-YSZ nanocrystalline granular film is really suitable for electromagnetic noise suppressor, which is applied in GHz.