Large magneto-optical birefringence of colloidal suspensions of α-FeOOH goethite nanocrystallites

- A magnetical birefringence (approximately 10−2) was observed for α-FeOOH suspensions.
- A model of optically equivalent ellipsoids is proposed to describe the behavior.
- Refractive index of the nanocrystallite is 103 times larger than that of the bulk.