Correlation Between Ferromagnetism And The Spin Mixing Conductance Of Permalloy

The new spintronic devices have high operation speed, low loss, non-volatile and other excellent features, and their development has aroused widespread concern in academic and industry. With the development of magnetic storage, the correlation between electron transport characteristics and spin has become increasingly important,on which the spin electronics are built in order to mainly study the spin generation,detection and regulation. From the general theories of LLG equation, General Ohm's law and inverse spin Hall Effect, the relationship among the spin rectification voltage?VSRE?, the inverse spin Hall voltage ?VISHE? and microwave magnetic field, sample magnetoresistance was expounded. By inverting of samples during test, the VSRE and VISHE were separated, with parameters like the ferromagnetic resonance linewidth,damping coefficient, spin Hall angle obtained, and the relationship between spin parameters and resistivity was studied.Firstly, NiFe and NiFe/Ta thin films were prepared on SiO₂ substrate by magnetron sputtering, and proper thermal treatment of the sample could improve the film magnetic performances, then the magnetic properties of the films that anisotropy magnetoresistance, resistance, surface roughness were tested. A conclusion can be drawn that the AMR of both NiFe and NiFe/Ta increased firstly and then decreased with temperature from 100 ? up to 500 ?, and both reached the maximum of 0.8 and 1.0 at 400 ?, respectively. And the half linewidth of AMR decreased gradually, because the atoms were arranged more orderly, with boundary scattering dropping, resulting in the decrease of resistivity under annealing, however, the roughness was increased due to the nonuniformity of the grain growth. In addition that interdiffusion would be generated at the interface during thermal treatment, and the thickness increased from 21.49 A up to 25.65 A, which would cause the thickness of inactive magnetic layer increased, and this in return affected magnetoresistance, and the density of each layer became larger, indicating that the defects of samples were reduced and samples were denser.Secondly, the photoelectric voltage of NiFe samples and NiFe/Ta samples were tested by a spin rectification test platform based on short-circuit microstrip lines, and inverting of samples during test separated the VSRE and VISHE, to obtain the ferromagnetic resonance linewidth, damping coefficient. The comparison of the results of NiFe and NiFe/Ta showed that the ferromagnetic resonance linewidth of NiFe/Ta sample was larger than that of NiFe sample at each frequency point, due to the presence of spin injection and symmetrical components in the measured voltage with magnetic field of NiFe/Ta sample weighted greater than that of monolayer because of the contribution of ISHE, but the intrinsic ferromagnetic resonance linewidth??H0? was less than 5 Oe in both NiFe and NiFe/Ta samples, indicating that the film inhomogeneity was small. This meaned that NiFe and NiFe/Ta films were of the same quality. Covering NiFe with Ta did not improve the film crustallization, thus making the performances of the sample comparable.Finally, the effect of NiFe/Ta electron transport on spin was discussed.Ferromagnetic film absorption power was obtained by Vector network analyzer,followed by the calculation of microwave magnetic field, spin Hall angle and spin mixed conductance. Then, the spin hall angle was calculated and it did not change with the frequency varing, indicating that the spin conversion efficiency had a close relation with the sample itself but had nothing to do with the wave frequency. Even though the theoretical model predicted that the square of the spin Hall angle was proportional to the conductivity, however, there was a significant difference between the experimental data and the theory. The spin mixing conductance gmix tot was calculated by comparison of the formula of ferromagnetic resonance linewidth with frenquency, and 9mix eff was calculated by the voltage of VISHE versus the magnetization precession cone angle. The trend of gmix totand gmix eff with resistivity were the same, fluctuating around 1×1019 m-2, on the basis of that, two theoretical methods, indicating the loss of the spin momenta in the ferromagnetic material was converted into the DC voltage by the Inverse spin Hall effect, and the spin mixing conductance was determined mainly by the nonmagnetic layer, rather than by the magnetic layer, which specified the direction for optimizing the photoelectric voltage of the material.