Magnetostatics And Magnetization Dynamics Of Ferromagnetic Thin Films

Magnetization of magnetic material would precess under radio-frequencyirradiation. The dynamics of magnetization precession is strongly influenced byfrequency, polarization and the material itself. Conventionally, researches use amicrowave cavity to realize the observation of microwave response forferromagnetic material. Several excitations, including ferromagnetic resonance andspin wave (magnon) excitations were widely investigated by this method. Other thantraditional cavity technique, electric detection based on microwave-assisteddirect-current effect in ferromagnetic samples has become an important method tostudy the magnetization dynamics during recent twenty years. Comparing to cavitytechnique, a great advantage for electric detection is its phase sensitivity: the lineshapes of direct-current spectra can reflect the precession phases with respect to theimposed microwave magnetic component.Ferromagnetic thin films can be treated as highly-compacted, phase-resolvedand sub-millimeter scaled electromagnetic wave sensors based on electric detectiontechnique. The purpose of our work demonstrated in this thesis is realizing aphase-and-polarization resolved microwave sensor. Based on the solution ofLandau-Lifshitz-Gilbert equation, demagnetization theory and research on magneticanisotropy, magnetostatics and magnetic dynamics in ferromagnetic thin films underradio-frequency irradiation are systematically investigated. Furthermore, we herebypropose a new technique that can be used for precisely measuring the saturatedmagnetization and demagnetization tensor in ferromagnetic microstrips. Byintroducing a new technique called electric detection and the rectification effect inmagnetic materials, a phase-and-polarization resolved electromagnetic wave sensorwith better power consumption and smaller volume is interpreted. We also interpret amethod to measure some basic physical features, such as saturated magnetization,magnetic anisotropy and demagnetization tensor in magnetic microstructures by utilizing electric detection as an ancillary method. Furthermore based on the electricdetection, we observed the spin wave excitation in low-dimentional magneticmicrostructures. Spin dynamics in spin wave excitation is also investigated based onthe direct-current spectra.