Ferromagnetic levitation and harmonic trapping of a milligram-scale Yttrium Iron Garnet sphere

TL;DR

This paper demonstrates passive magnetic levitation and harmonic trapping of a milligram-scale Yttrium Iron Garnet sphere at cryogenic temperatures, combining magnetic and diamagnetic effects, with potential for multi-physics interactions.

Contribution

It introduces a novel passive magnetic levitation technique for a millimeter-scale YIG sphere, integrating magnetic and diamagnetic trapping methods at cryogenic temperatures.

Findings

Achieved stable levitation of a 0.3 mg YIG sphere at 4 K.

Measured trapping frequencies up to 600 Hz and Q-factors around 10^3.

Validated experimental results with finite element simulations.

Abstract

We report passive magnetic levitation and three-dimensional harmonic trapping of a 0.3 milligram, 0.5 millimeter diameter Yttrium Iron Garnet sphere at 4 K. The gradient of an external magnetic field is used for vertical trapping, while the finite size effect of the diamagnetic effect is used for horizontal trapping. The dynamics of the levitated sphere was optically measured to have trapping frequencies of up to around 600 Hz and mechanical $Q$-factors in the order of $Q \sim 10^3$. These results were quantitatively reproduced by three-dimensional finite element method simulations. Our results can provide a novel system where magnetism, rigid body motions, microwaves, and optics interact.