Achieving giant magneto-optical birefringence is a long-standing goal in view of its intriguing physics and potential applications in transmitted light modulation. Due to the unique geometric features of two-dimensional materials with extremely large shape anisotropy, the resultant couplings among magnetic, electric, and optical properties enable giant magneto-optical birefringence effects, as represented by a record-breaking magneto-optical Cotton–Mouton coefficient in two-dimensional material systems. In this Perspective, we introduce the discovery of the giant magneto-optical birefringence effect in two-dimensional metal oxide dispersion in 2020, followed by analyses of the underlying mechanisms. We then discuss how the interplay of anisotropy and colloidal behavior affects the Cotton–Mouton effect. Finally, we proceed to potential applications and give our ideas about future developments in this emerging field.

Ferromagnetism with perpendicular magnetic anisotropy (PMA) receives continuous attention. But, the PMA is always limited by materials system, the assistance from suitable buffer layers such as Pt and Ta is essential. A general method for the generation of PMA on various systems is pursued. Herein, it is shown that preparatory plasma etching of oxide substrate produces robust PMA in subsequent grown ferromagnetic multilayers, out‐of‐plane hysteresis loop is rectangular with remanence close to 100%. In contrast, without the preparatory plasma etching, out‐of‐plane hysteresis loop of subsequent grown ferromagnetic multilayers is very oblique, the calculated uniaxial anisotropic constant is one order of magnitude smaller than the former one. The enhancements of PMA are observed in distinct oxide substrates including Si/SiO2, Al2O3, LaAlO3, and MgO, indicating the interfacial plasma etching technique can be used for various oxide substrates to obtain PMA. The promotion of Co–O hybridization is proposed to be the dominant reason for the enhancement of PMA, which is supported by the control experiment. This finding provides opportunity for the formation of interfacial PMA on crystalline oxide substrates, and expands the material selection for achieving PMA.

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