Bismuth-substituted Lutetium Iron Garnet Films with Giant Visible-Range Magneto-Optical Sensitivity

Abstract

Magneto-optical materials are indispensable across modern physics, serving as the foundation for precision magnetic sensing, nonreciprocal photonics, and optical isolation technologies. The continual pursuit of materials with high Verdet constants has driven the development of garnet-based compounds exhibiting extreme magneto-optical sensitivity. In this work, we report the growth and comprehensive magneto-optical characterization of bismuth-substituted lutetium iron garnet (LuBiIG), a material that combines the large spin-orbit coupling of bismuth with the lattice stability of lutetium iron garnet. The films exhibit an exceptionally high Verdet constant of up to -0.120 deg/um/mT, peaking in the visible spectral range near 520nm. LuBiIG films with thicknesses between 80 and 220nm were grown by pulsed laser deposition and characterized at room temperature over the 500-820nm wavelength range. These results position LuBiIG as a highly sensitive magneto-optical material suitable for advanced cryogenic detection and hybrid quantum applications.

Figures (2)

• Figure 1: Longitudinal MOKE hysteresis loops for the series of LuBiIG samples. Each curve is normalized to its maximum intensity. Note that the magnetic field range (x-axis) differs between panels to highlight the variation in saturation behavior.
• Figure 2: (a) Representative Faraday hysteresis loop of sample 8 measured at a wavelength of 600nm. The contribution from the GGG substrate is subtracted from the raw data (dashed red line), and the linear regions of the corrected curve (solid red line) are fitted to extract the saturation field. (b) Repeated hysteresis measurements at several wavelengths on a demagnetized sample over a reduced field range. The fitted slope is used to determine the Verdet constant. (c) Wavelength dependence of the Verdet constant for all LuBiIG films, exhibiting a pronounced maximum in absolute value at 520--530nm.