Magneto‐Optical Kerr Effect and Ultrafast Demagnetization in the Bi, Mn: YIG Films with Perpendicular Magnetic Anisotropy

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The magneto‐optical Kerr effect (MOKE) reflects the spin‐orbit coupling in magnetic materials, so it can become a fundamentally important tool for studying the electronic structure of materials. Here the MOKE, and the ultrafast demagnetization process is presented for Bi and Mn‐doped Y3Fe5O12 films with perpendicular magnetic anisotropy. The structural characterization indicated horizontal dipping has a large growth rate compared to vertical dipping, which will reduce cracks and improve the crystal quality. By analyzing the MOKE signals in different magnetic field directions and comparing them with the theoretical equations, it can be found that the quadratic MOKE values of YIG samples originate from the large perpendicular magnetic anisotropy previously described in YIG samples. Time‐resolved MOKE measurements show that with increasing Bi3+ content, the spin‐orbit coupling is enhanced, which results in the spin‐lattice relaxation time constants becoming smaller, and the magnetization recovery processes are accelerated.