Orientation-Controlled Bi26− x − y Co x Fe y O40/MgO/Si Thin F
Cheng Wang, Jiafang Xie, Teng Gao, Yufeng Xie, Lingbo Zhou, Yuling Lin, Ziwei Wang, Junying Wu, Qinyu Cao, Bowen Zhang, Xiaolin Hu, Naifeng ZhuangAbstract
Integrated nonreciprocal optical devices on silicon (Si) remain challenging because interdiffusion at the magneto-optical (MO) film/Si interface degrades film quality and weakens optical performance. Here, we insert an MgO buffer layer between the Si substrate and Bi26-x-yCoxFeyO40 (BCFO) thin films deposited by radio-frequency (RF) magnetron sputtering. Structural and interfacial characterizations show that MgO effectively suppresses interdiffusion of Si and Fe/Co, as well as promotes a preferred orientation in BCFO. Consequently, MgO-buffered films exhibit markedly improved properties: the surface roughness decreases by 38%, the saturation magnetization increases to 1.5 times its original value and the magnetic circular dichroism (MCD) signal increases by approximately fivefold. These results highlight the potential of MgO-buffered BCFO films for practical nonreciprocal optical devices.