Nanometer thick iron garnet films with high Faraday rotation

Abstract

Here we demonstrate nanometer thick iron garnet films with high specific Faraday rotation suitable for the magneto-optical applications. Bismuth-substituted iron garnet films of compositions Bi1Y2Fe5O12 and Bi1Tm2Fe5O12 deposited on gadolinium gallium garnet substrate are fabricated and characterized. Their thicknesses range from 2 to 10 nm, which corresponds to just a few crystal lattice constants. Spectacularly, Faraday rotation of the 2 nm thick Bi1Y2Fe5O12 film reaches 29.3deg/µm at 420 nm that is comparable to the single crystal micrometer thick films of similar composition. The film surface morphology by atomic force microscopy gives root mean square (RMS) roughness of the nanometer thick films as small as 0.13 nm that is also similar to the RMS of single crystal micrometer thick films. Moreover, the 3 nm thick Bi1Tm2Fe5O12 films demonstrate a pronounced effective uniaxial anisotropy. These all make the fabricated nanometer thick films very promising for their potential applications in magneto-optical devices and quantum technologies.