Orientation-Controlled Bi26-x-yCoxFeyO₄₀/MgO/Si Thin Films: Enhanced Magneto-Optical Performance.

(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.