Studies On The Preparation And High Frequency Magnetic Properties Of FeSi Alloy Thin Films

FeSi compunds are widely used in electronics, optoelectronics, thermalelectronic and magnetism fields due to its excellent magnetic and electric properties. With the development of the intelligent, digiminiature, miniature and high frequency devices, thin films are required. Because of its excellent magnetic properties, FeSi thin films are widely used in the high frequency magnetic devices. Therefore, it is very necessary to study the high frequency magnetic properties of FeSi thin films.FeSi thin films were prepred by magnetron sputtering in this thesis. The influences of the substrates, sputtering power and annealing temperature on the microstructures, static magnetic properties and spin rectification voltage of FeSi thin films were investigated. Firstly, FeSi thin films were deposited on glass substrates with sputtering pressures of 0.6Pa, 0.8Pa, 1.0Pa, 1.2Pa and 1.4Pa. The results show that the saturation magnetization Ms of the FeSi thin films increases firstly and then decreases with the increase of sputtering pressure. The Ms reaches its maximum value of 15543.52 Gs when the sputtering pressure is 1.0Pa.We grow FeSi thin films on Si(100) substrates with sputtering powers of 20 W, 40 W, 60 W, 80 W and 100 W. The results show that the FeSi thin films deposited on the Si substrates have different degrees of crystallization and the diffraction peaks of Fe3Si(200), Fe3Si(220) are observed. In the sputtering power range from 20 W to 100 W, the saturation magnetization Ms increases firstly and then decreases. The Ms reaches its maximum value of 10509.24 Gs when the sputtering power is 60 W. The ferromagnetic resonance linewidth ?H decreases from the maximum value of 351.21 Oe to the minimum value of 69.18 Oe with the increase of sputtering power at 4GHz.In order to study the effects of annealing temperature on the properties of FeSi thin films, the as-deposited FeSi thin films with sputtering power of 40 W and 100 W are annealed at 200℃, 300℃, 400℃, 500℃ and 600℃. The crystallization degree of FeSi thin films with sputtering power of 40 W increases with the increase of annealing temperature. The effects of annealing temperature on crystallization is very small when the annealing temperature is over 400℃. Compared with the as-deposited samples, the Ms of the annealed sample increases. With the increase of annealing temperature, Ms increases firstly and then decrases. The Ms reaches its maximum value of 14417.18 Gs when the annealing temperature is 400℃. The ferromagnetic resonance linewidth ?H decreases from the maximum value of 461.79 Oe to the minimum value of 177.18 Oe with the increase of annealing temperature at 4GHz. For the FeSi thin films prepared under high sputtering power of 100 W, annealing temperature has little effects on its crystallization degree. The Ms decreases gradually from 10361.46 Gs to 8320.1Gs with the increase of annealing temperature. The ferromagnetic resonance linewidth ?H decreases obviously from the maximum value of 277.91 Oe to the minimum value of 158.24 Oe with the increase of annealing temperature at 4GHz.In the spin rectification effects measurements, it is found that the noise is high because the microwave magnetic field of the microstrip fixture is weak. In this thesis, microwave cavity if designed and fabricated to measure the spin rectification effects of the ferromagnetic films. The results show that larger signal and signal to noise ratio are achieved with this microwave cavity.