Experimental investigation of nonuniform rotation of the magnetization vectors in iron garnet single crystal films

The properties of nonuniform rotation of the magnetization vectors in epitaxial single crystal iron garnet films are studied experimentally in pulsed magnetic fields up to 2000 Oe. An experimental arrangement is set up which involves electron-optical chronography with which rapid processes in thin magnetic films can be studied in a real time scale with a time resolution of approximately 60 ps. By means of this apparatus a study is made of the nonuniform rotation of the magnetization vector at arbitrary points of the sample and for various orientations and intensities of the external magnetic fields. The feasibility of determining the remagnetization times at local points in the magnetic films is demonstrated. It is found that the local regions in the sample can be remagnetized in a time less than 1 ns. It is found experimentally that due to the finity of the proper relaxation times of the magnetic moments the system under investigation is too slow to ''follow'' the changes in the external magnetic fields if these occur with nanosecond time characteristics. The rate of the nonuniform rotation process depends strongly on the strength of the pulsed or stationary magnetic fields in the plane of the sample. The features of the formation and motion of the magnetic moment flip waves (MMFW) are investigated in detail. The velocity of the MMFW is found to be proportional to deltaHsub(pul)/deltat and to the spatial gradient, i.e, deltaHsub(pul)/deltar. As a rule, the MMFW width varies between tens and hundreds of microns depending on the intensity and direction of the external magnetic fields. In multilayer iron garnet films in the initial stages of nonuniform rotation the MMFW may be formed consecutively with a time interval approximately 0.5-1 ns. It is found that in one of the layers fof the sample and in a strong gradient field practically uniform rotation of the magnetization vectors may occur