Imaging Magnon Excitation with Spin-Polarized Scanning Tunneling Microscopy

Inelastic electron scattering plays a crucial role in spintronics devices concerning the spin lifetime of polarized electrons and the amount of spin transfer torque for switching magnetic configurations in magnetic tunnel junctions. One of the fundamental processes is magnon creation, which occurs when injected hot electrons induces spin-flip scattering with an electron in the Fermi sea of the magnetic material. To image and address the magnetic origin of the excitations, we have performed low-temperature spin-polarized inelastic electron tunneling spectroscopy (IETS) on double layer (DL) Mn thin films formed on W(110) substrate.
The atomically-thin magnetic layer exhibits homogeneous spin spiral with antiferromagnetic coupling, which provides a good reference for spin-polarized scanning tunneling microscopy (STM). Characteristic peak-dip feature in IETS as well as its correlation with the spin spiral are acquired. Additionally, we have observed contrast reversal in the IETS intensity when the tip magnetization direction is flipped, indicating that the excitation is spin-dependent and thus presumably due to magnon creation. The spatial distribution of the magnon excitation and its energy dependence will be discussed in the presentation.