Regulation Of Dynamic Damping By Antiferromagnetic Coupling At The Interface Of Ferromagnetic/nonmagnetic Bilayers

Magnetic film is an important part of spintronics devices,which properties largely determine the performance of the related devices.Magnetic damping plays a critical role in the magnetization dynamic behaviors of magnetic media for the modification of response speed.The spin pumping effect is an effective way to regulate the dynamic damping in magnetic films without destroying the fine magnetism.In the past,many theories and experiments have shown that the ferromagnetic/non-magnetic(FM/NM)interface can regulate the magnetic damping factor of the ferromagnetic layer.In this paper,the rare earth metal gadolinium(Gd)is used as the capping layer to study the variation of dynamic damping factor with the thickness of the capping layer,and the control of spin pumping by interface effect is obtained.The effect of the Ni₈₀Fe₂₀(Py)/Gd interface on the damping factor is proved by using the insertion layer with different thickness.At the same time,the spin-pumping effect of Py/Fe Mn is compared to further understand the mechanism of the effect of interfacial antiferromagnetic coupling on the damping factor.The main research as follow:1.In the Py/Gd bilayer system,with the increase of Gd thickness,the magnetization damping factor increases rapidly at first,and then tends to be stable.The stable value reaches13×10³,which is 1.5 times of that of single-layer Py;The corresponding saturation magnetization decreases with the increase of Gd thickness in a certain range of Gd thickness.If the enhancement of the magnetization damping factor is attributed to the spin pump,the dependence of the magnetization damping factor on the thickness of Gd layer is fitted by the spin pump theory,and the interface spin mixed conductivity is 1.32×10¹⁵cm^-2 and the spin diffusion length of Gd is 8 nm.The Cu layer is inserted into the interface of Py/Gd bilayers.It is found that only 1 nm Cu intercalation could significantly inhibit the decrease of magnetization of Py/Cu/Gd bilayers,and the rising trend of magnetization dynamic damping factor is also slowed down,which indicated that the insertion of Cu layer inhibited the interface effect induced magnetism and destroyed the antiferromagnetic coupling interface.Due to the magnetic proximity effect,Py induces the reverse magnetic moment of Gd at the interface,which leads to the decrease of magnetization.The antiferromagnetic coupling interface enhances the spin pumping effect.2.Significant exchange bias is observed in Py/Fe Mn,and the critical thickness of Fe Mn for exchange bias is as low as 2 nm.The variation trend of the magnetization damping factor of Py/Fe Mn with the thickness of Fe Mn is similar to that of Py/Gd with the thickness of Gd.The dependence of the magnetization damping factor on the thickness of the Fe Mn layer is fitted by using the spin pump theory,and the interface spin mixed conductance is3.23×10¹⁵cm^-2 which is higher than that of the antiferromagnetic interface induced by Py/Gd.The spin diffusion length of Fe Mn is 13 nm,which is longer than that of Gd.It is found that the resonance linewidth of Py/Fe Mn(2 nm)/Cu is almost the same as that of Py/Gd(1-2nm)/Cu at all measurement frequencies,but the magnetization damping factor can be greatly increased by 4 nm Fe Mn intercalation,which indicates that the antiferromagnetic coupling strength of Py/Gd interface is lower than that of Py/Fe Mn interface.It shows that the two kinds of interface coupling are different in essence.