Tunable spin dynamic damping and interfacial spin transparency in Py/Ho through magnetic field modulation

Spin transmission is critical for the functionality of logic circuits, magnetic random-access memories, and magnetic sensors. Rare earth (RE) metals, which are promising candidates for tuning spin transmission, can form antiferromagnetically coupled interfaces with ferromagnetic layers. In this study, we investigate the laser-induced ultrafast spin injection from permalloy (Py) into the RE metal holmium (Ho), modulated by interfacial engineering and varying the external magnetic field strength. The antiferromagnetically coupled interface between Py and Ho is confirmed by x-ray magnetic circular dichroism, and its correlation with spin dynamic damping is revealed by time-resolved magneto-optical Kerr effect. More importantly, we demonstrate the effective modulation of spin transmission through an external magnetic field. At the Py/Ho interface, a substantial spin-mixing conductance (SMC) of approximately 7.71 × 1015 cm−2 is observed, which can be modulated by approximately 35% under an external magnetic field. The applied high magnetic fields are found to suppress the large SMC, primarily due to the modified sperimagnetic structure at the Py/Ho interface. These findings demonstrate the excellent spin transmission efficiency in the Py/Ho system, providing a promising approach for magneto-dynamics modulation in spintronic devices.