Helicity‐Dependent All‐Optical Switching in Bi,Ga‐Substituted Rare‐Earth Iron Garnet Films Driven by Orbital Magnetic Moment

ABSTRACT All‐optical magnetization switching (AOS) is a promising phenomenon for applications such as high‐speed optical modulation technologies, as it enables magnetization switching using only ultrashort laser pulses. AOS induced by circularly polarized light is demonstrated in Bi, Ga‐substituted iron garnet thin films, Bi,Ga: R IG (rare earth R = Eu 3+ , Nd 3+ , and Y 3+ ), which exhibit both a large Faraday effect and perpendicular magnetic anisotropy. The AOS experiments are performed using various numbers of laser pulses and fluences, with a wavelength of 514 nm and a pulse width of 230 fs. Ring‐shaped magnetic domains appear in the vicinity of the demagnetized regions. We find that helicity‐dependent switching for the sample with R = Eu 3+ is more efficient than that for R = Nd 3+ . Soft X‐ray magnetic circular dichroism measurements indicate the orbital magnetic moment of both R = Eu 3+ and Nd 3+ , suggesting a correlation between helicity‐dependent AOS in the garnet films and the 4 f orbital magnetic moments of R ions. These findings provide a material design strategy to enhance helicity‐dependent AOS by controlling the orbital magnetic moments through rare‐earth substitution.