Giant and controllable in-plane spin angular shifts in bulk and ultrathin magnetic materials

Abstract

The magneto-optical Kerr effect (MOKE) refers to the rotation of the polarization plane when a linearly polarized light is reflected at the surface of magnetic material. The MOKE reveals the magnetization of the optical properties of magnetic material and can be characterized by the dielectric tensor containing the magneto-optical constant. Thus, exploring the MOKE requires very precise determination of the magneto-optical constant. The photonic spin Hall effect (PSHE), which corresponds to the lateral and in-plane spin-dependent splitting of the beam, can be used as an effective method to characterize the magneto-optical constant due to its advantage of being extremely sensitive to changes in the physical parameters of the material. Most of the previous studies only considered the case of a single thickness of magnetic material and a single MOKE and need to introduce complex weak measurement techniques to observe the photonic spin Hall effect. In this work, we theoretically investigate the in-plane spin angular shifts in three MOKE cases in bulk and ultrathin magnetic materials. We can effectively tune the in-plane angular displacements of different magnetic material thickness by changing the magnetic field direction corresponding to different MOKEs and changing the magneto-optical constants (including amplitude and phase). The research results show that in the case of bulk and ultrathin magnetic materials, the internal spin angular displacements under different MOKEs will show different trends when the magneto-optical constants change the amplitude and phase, especially in ultra-thin magnetic material. In the lateral Kerr effect in thin material, the photon in-plane angular displacement does not affect the change of the magneto-optical constant, but in other cases, the amplitude relative to the phase has a much larger effect on the photon in-plane angular displacement. In this regard, we propose a new method which can directly determine the amplitude and phase of the magneto-optical constant by using the huge in-plane spin angular displacement without considering the weak measurements and can also judge different MOKEs according to the variation of the in-plane angular displacement in the bulk and ultrathin magnetic materials. This method not only provides a new probe for measuring magneto-optical constants but also expands the study of spin photonics.