Soft Magnetism And High Frequency Properties Of [Fe₆₅Co₃₅/ZnO]_n Multilayer Films

With the rapid development of social economy, the electronic products gradually tend to be miniaturization and high frequency operation. In order to satisfy the demand of magnetic electronic components, we use semiconductor materials to replace previous insulation materials to prepare the ferromagnetic metal/semiconductor multilayer on glass substrates and silicon substrates. In this paper, [Fe65Co35/ZnO]n multilayer films were prepared by direct current(dc) and radio frequency(rf) magnetron sputtering. Their physical properties were measured by using X-ray diffraction(XRD), high resolution transmission electron microscopy(HRTEM) and vibrating sample magnetometer(VSM), dc four-probe method and vector network analyzer to systematically study the structures, the microstructures, the magnetic and electrical properties of the samples. The research results are listed as follows:X-ray diffraction(XRD) results show that with the gradual increase of semiconductor ZnO layer thickness t, the crystallization of ZnO is getting better and better. Metal particles are in the state of face-centered cubic crystal structure, and the particle size of Fe65Co35 decreases from 3.4 nm to 2.7 nm. For the tilted sputtering[Fe65Co35/ZnO]50 multilayer film, the resonance frequency fr were above 4 GHz and almost remained the same with the increasing t. This is due to the common effect caused by the increase in thickness of ZnO layer which makes saturation magnetization of the thin films decrease and the dynamic anisotropy fields increase.For the typical sample t = 3.5 nm, the resistivity is up to 2420 ???cm. The ?'2g and?'3g decrease with the increasing t. But ?'2g is still greater than 90, and ?"2g keeps a low value(< 1.55). Therefore, when the external frequency is above 2 GHz, quality factor Q is more than 150, and it is even greater than 2.6 when the external frequency is up to 3 GHz. So high resistivity and quality factor suggest that the samples have better high frequency applications.In addition, the effects of different underlayers on soft magnetic properties and high frequency properties of the thin films were also studied. FeNi underlayer can contribute to the exchange coupling effect with the ferromagnetic metal layer and thus making samples obtain a larger in-plane uniaxial anisotropy field. While the ZnO underlayer will affect the continuity of the ferromagnetic layers in the multilayer films,forming a little bigger coercivity.