磁性薄膜的L-S耦合研究
發(fā)布時間：2018-08-23 19:42
【摘要】：坡莫合金Py(Py=Ni80Fe20)作為重要的軟磁材料,具有低矯頑力、低磁各向異性、低阻尼因子等特點,廣泛的應用于自旋電子學的研究中。而過渡重金屬元素鉑(Pt),銀(Ag),金(Au)具有較大的自旋軌道(L-S)耦合作用,可以通過與Py的摻雜,修飾或影響自旋電子學器件的磁學性質。因此,本論文以坡莫合金-重金屬摻雜薄膜為主要研究對象,系統(tǒng)地研究了不同摻雜濃度的Py100-xMx薄膜(M = Pt,Ag,Au)和Py100-x-yPtxAgy薄膜的磁動力學性質的調控以及采用以上薄膜制備的自旋霍爾振蕩器件的微波傳輸性質。主要研究結果包括以下幾個方面:1.一元摻雜Py100-xMx合金薄膜(M = Pt, Ag, Au)的磁動力學參數(shù)隨摻雜濃度和摻雜元素的變化。系統(tǒng)研究了 Py100-xMx薄膜的磁靜態(tài)、動態(tài)性質,研究發(fā)現(xiàn):(1)Py100-xAgx或Py100-xAux系列薄膜的阻尼因子隨著摻雜組分的增加而呈現(xiàn)出線性增強趨勢,而Py1oo-xPtx系列薄膜呈現(xiàn)出一個二次平方的關系行為。和摻雜元素Ag和Au相比,當Py摻雜進Pt時,Pt對阻尼因子有最大的影響,Py70Pt30薄膜的阻尼因子α =0.035是純Py單層薄膜阻尼因子的4.5倍大。另一方面,Py100-xAgx薄膜的阻尼因子幾乎和摻雜的Ag濃度變化不相關;(2)Py100-xMx薄膜的飽和磁化強度Ms隨著摻雜濃度的增加而顯示了一個二次元方程的遞減關系趨勢,減小最快的是Au而減少最慢的是Pt; (3)Py100-xMx薄膜的交換勁度系數(shù)A隨著摻雜濃度的增加而呈現(xiàn)出線性遞減的趨勢,其中Py100-xAgx和Py100-xAux薄膜的A下降的相對較快。該動力學參數(shù)的實驗趨勢與DFT理論計算的結果一致符合。通過變溫鐵磁共振儀研究了不同摻雜金屬及濃度對Py100-xMx薄膜磁性的溫度依賴關系的變化影響。實驗發(fā)現(xiàn)Py100-xMx薄膜的阻尼因子隨著溫度的增加而增加,其中Py70Au30的增幅最大。通過自旋駐波模式的頻率依賴性能夠得到自旋波常數(shù)D, D的溫度依賴性能夠通過T2定律描述,顯示了薄膜材料中顯著的電子的巡游特性。同時對Ms的溫度依賴性進行了測量和擬合,并通過Bloch定律估算了自旋波常數(shù)D,比較兩種擬合方法研究了 Pyio0-xMx磁性薄膜的可能內在激發(fā)機制。2.二元摻雜Py1oo-x-yPtxAgy薄膜,定義三維的參數(shù)空間,在一定的范圍內調控其MS,α和A獨立變化。為了獨立調控坡莫合金的磁性,成功設計了合金薄膜系統(tǒng)Py100-x-yPtxAgy,通過調制Pt和Ag的摻雜組分,保持飽和磁化強度MS不變,提高阻尼因子的設想。成功的制備了厚度為100 nm的Py100-x-yPtxAgy薄膜,實現(xiàn)了平均飽和磁化強度保持為μ0MS=0.724± 0.014 T,而阻尼因子隨著Pt組分的增加而有接近4倍的增長。3. Py100-x-yPtxAgy/Pt - SHNO器件-單納米壓縮結構。以二元摻雜的Py100-x-yPtxAgy薄膜為基礎,設計和制備了 Py84Ag16/Pt(S01),Py77.5Pt10Ag12.5/Pt (S02), Py75Pt15Ag10/Pt (S03),Py73Pt19Ag8/Pt (S04)雙層薄膜,該系列薄膜的飽和磁化強度μ0Meff = (0.617±0.034) T,阻尼因子的可調控范圍為1-3倍左右。在上述薄膜基礎上,成功的制備了單納米壓縮結構的SHNOs器件,壓縮結構具有相同寬度150nm。研究發(fā)現(xiàn),在同一磁場0.5T下,固定磁場掃電流IDC,(1)不斷增加的阻尼因子不會改變器件所激發(fā)自振蕩模式的電流-頻率依賴關系;(2)在自振蕩行為發(fā)生之后,峰寬Δf急劇變窄,且隨著IDC的不斷增加而趨于平穩(wěn)狀態(tài)。低阻尼因子S01器件的最小峰寬Δf～ 9.6 MHz,而其他較高阻尼因子器件具有更小的峰寬,Δf～ 3 MHz; (3) SHNOs器件的輸出功率P均隨著IDC的增加而以指數(shù)的形式增加,但是隨著器件阻尼因子的增大,P出現(xiàn)了明顯的下降;(4)自振蕩發(fā)生的臨界電流IDCth幾乎隨著阻尼因子的增大而線性增加。(5)對比分析不同外加磁場與臨界電流IDCth在的變化關系,SHNO器件的阻尼因子越小而在越高的外加磁場下,越有利于器件保持激發(fā)自振蕩狀態(tài)。在同一掃描電流3.2mA下,固定電流掃磁場μ0Hex,(1)自振蕩頻率隨著外加磁場的增加而不斷增加,符合面外磁場與振蕩頻率的關系規(guī)律,且由于器件的飽和磁化強度均相同,自振蕩峰頻率與外加掃描磁場的變化關系基本一致;(2) SHNOs器件的輸出功率P與磁場的變化關系相似,首先隨著外加磁場的增加而增大,在中間磁場時達到峰值,最后相對下降,直到?jīng)]有自振蕩被觀測到為止。SHNOs器件產(chǎn)生的最大輸出功率隨著阻尼因子的增大而單調遞減;(3)最小峰寬隨著增加的阻尼因子也呈現(xiàn)單調遞減的趨勢。4. Py100-x-yPtxAgy/Pt - SHNO器件-雙納米壓縮結構。在相同的薄膜結構和單納米壓縮器件的基礎上,制備了雙納米壓縮結構的SHNOs 器件 Py84Ag16/Pt(D01),Py77.5Pt10Ag12.5/Pt(D02),Py75Pt15Ag10/Pt(D03),Py73Pt19Ag8/Pt(D04)。研究了 SHNOs器件的性能隨著掃描電流的變化。在同一磁場下,(1)當固定SHNOs器件的雙納米壓縮結構間隔(dcc = 300 nm)時,隨著阻尼因子的不斷增加,互同步性減弱或消失,輸出功率減弱,峰寬增大。SHNO器件的互同步狀態(tài)的峰寬不但比未同步態(tài)的要小很多,而且互同步狀態(tài)的輸出功率要比兩個單獨未同步態(tài)下的輸出功率之和還要大;(2)當改變雙納米壓縮結構的間距(dcc= 300nm,600nm,900nm)來觀察SHNOs器件的互同步狀態(tài)變化時,低阻尼因子的D01器件能夠在間距為300 nm和600 nm的情況下觀察到互同步狀態(tài),而稍高阻尼因子的D02器件只能在間距為300 nm的情況下觀測到互同步狀態(tài),對器件D03和D04來說,未在任何間距下觀測到互同步狀態(tài)。5.Py84Ag16/Pt-SHNO器件-多納米壓縮結構。在Py84Ag16/Pt的雙層膜結構上制備一列5個等間距納米壓縮結構的SHNO器件,與雙納米壓縮結構的Py84Ag16/Pt-SHNO器件結果對比,同一磁場6000 Oe下,相同寬度的納米壓縮結構,間距也同為300 nm時,得到的最大輸出功率要大2倍多;并且在磁場為7000 Oe下,最大輸出功率高達17pW,最小峰寬小于1MHz。
[Abstract]:As an important soft magnetic material, permalloy Py (Py = Ni80Fe20) is widely used in spintronics because of its low coercivity, low magnetic anisotropy and low damping factor. The transition heavy metal elements Pt, Ag and Au have large spin-orbit (L-S) coupling effect and can be modified or influenced by Py doping. Magnetic properties of spintronics devices. Therefore, in this paper, we systematically studied the magnetodynamic properties of Py100-xMx thin films (M=Pt, Ag, Au) and Py100-x-yPtxAgy thin films with different doping concentrations and the micro-scale spin Hall oscillator devices fabricated by the above thin films. The main results are as follows: 1. The magnetodynamic parameters of Py100-xMx alloy films (M = Pt, Ag, Au) doped with Py100-xMx as a function of doping concentration and doping elements. The magnetic static and dynamic properties of Py100-xMx films are studied systematically. The results show that: (1) the damping factors of Py100-xAgx or Py100-xAux films vary with doping concentration and doping elements. The Py_ 1oo_ xPtx thin films exhibit a quadratic square relationship with the increase of doping composition. Compared with the doping elements Ag and Au, Pt has the greatest influence on damping factor when Py doped into Pt. The damping factor of Py_ 70Pt_ 30 thin films is 4.5 times larger than that of pure Py single layer films. The damping factor of Py100-xAgx thin films is almost independent of the concentration of A g doped in Py100-xMx films; (2) The saturated magnetization of Py100-xMx thin films M shows a decreasing trend of quadratic element equation with the increase of doping concentration, the fastest decreasing trend is Au and the slowest decreasing trend is Pt; (3) The exchange stiffness coefficient A of Py100-xMx thin films decreases with the doping concentration. The experimental trend of the kinetic parameters coincides with the results calculated by DFT theory. The temperature dependence of the magnetic properties of Py100-xMx thin films with different doping metals and concentrations is studied by a temperature-dependent ferromagnetic resonance. It is found that the damping factor of Py100-xMx film increases with the increase of temperature, and Py70Au30 has the greatest increase. The spin wave constant D can be obtained by the frequency dependence of spin standing wave mode. The temperature dependence of D can be described by T2 law, showing the significant electron traveling characteristics in the film material. The spin-wave constant D was estimated by Bloch's law. The possible intrinsic excitation mechanism of Pyio0-xMx magnetic thin films was studied by comparing the two fitting methods. 2. Binary doped Py1oo-x-yPtxAgy thin films were characterized by defining three-dimensional parameter space and adjusting their MS, alpha and A independent variations in a certain range. Py100-x-yPtxAgy thin film system was successfully designed by adjusting the magnetic properties of permalloy. By adjusting the doping components of Pt and Ag, the saturated magnetization of Py100-x-yPtxAgy thin film with 100 nm thickness was kept unchanged and the damping factor was increased. Py100-x-yPtxAgy/Pt-SHNO device-single nano-compression structure. Py84Ag16/Pt (S01), Py77.5Pt10Ag12.5/Pt (S02), Py75Pt15Ag10/Pt (S03), Py73Pt198/Pt (S04) bilayer films were designed and fabricated on the basis of binary doped Py100-x-yPtxAgy thin films. The saturation magnetization of the films is 0 Meff = 0.617 (+ 0.034) T, and the damping factor is about 1-3 times as large as that of the films. On the basis of the above films, a single nano-compression SHNOs device with the same compression width of 150 nm has been successfully fabricated. Ne factor does not change the current-frequency dependence of the self-oscillation mode excited by the device; (2) After the self-oscillation behavior occurs, the peak width f becomes narrow sharply and tends to be stable with the increase of IDC. The minimum peak width f~9.6 MHz of the S01 device with low damping factor is smaller than that of the other devices with higher damping factor, and F is smaller. (3) The output power P of SHNOs devices increases exponentially with the increase of IDC, but decreases obviously with the increase of damping factor. (4) The critical current IDCth of self-oscillation increases linearly with the increase of damping factor. (5) Comparison and analysis of different applied magnetic fields and critical current IDCth. Under the same scanning current of 3.2mA, the constant current sweep magnetic field mu 0Hex, (1) the self-oscillation frequency increases with the increase of the applied magnetic field, which conforms to the relationship between the out-of-plane magnetic field and the oscillation frequency. As the saturation magnetization of the device is the same, the relationship between the peak frequency of self-oscillation and the variation of the applied magnetic field is basically the same. (2) The relationship between the output power P and the magnetic field of the SHNOs device is similar. First, the output power P increases with the increase of the applied magnetic field, reaches the peak value in the intermediate magnetic field, and finally decreases relatively until no self-oscillation is observed. Up to now, the maximum output power of SHNOs devices decreases monotonously with the increase of damping factor; (3) the minimum peak width decreases monotonously with the increase of damping factor. (4) Py100-x-yPtxAgy/Pt-SHNO devices-double nano-compression structures. On the basis of the same thin film structure and single nano-compression devices, double nano-particles were prepared. Squeezed SHNOs devices Py84Ag16/Pt (D01), Py77.5Pt10Ag12.5/Pt (D02), Py75Pt15Ag10/Pt (D03) and Py73Pt19Ag8/Pt (D04). The performance of SHNOs devices varies with scanning current. The peak width of the intersynchronous state of the SHNO device is much smaller than that of the unsynchronized state, and the output power of the intersynchronous state is larger than that of the two separate unsynchronized states. (2) When the distance between the two nanostructures is changed (dcc = 300 nm, 600 nm, 900 nm) The D01 device with low damping factor can observe the state of mutual synchronization at the spacing of 300 nm and 600 nm while the D02 device with slightly higher damping factor can only observe the state of mutual synchronization at the spacing of 300 nm. For D03 and D04, mutual synchronization is not observed at any spacing. Py84Ag16/Pt-SHNO device-multi-nano-compression structure.A series of five uniformly spaced nano-compression SHNO devices were fabricated on Py84Ag16/Pt bilayer film structure.The results were compared with those of Py84Ag16/Pt-SHNO device with double nano-compression structure.The nano-compression structures with the same width and spacing of 300 nm were obtained under the same magnetic field 6000 Oe. The maximum output power is more than twice as large, and the maximum output power is as high as 17 pW and the minimum peak width is less than 1 MHz under the magnetic field of 7000 Oe.
【學位授予單位】：東南大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：O484
本文編號：2199721
[Abstract]:As an important soft magnetic material, permalloy Py (Py = Ni80Fe20) is widely used in spintronics because of its low coercivity, low magnetic anisotropy and low damping factor. The transition heavy metal elements Pt, Ag and Au have large spin-orbit (L-S) coupling effect and can be modified or influenced by Py doping. Magnetic properties of spintronics devices. Therefore, in this paper, we systematically studied the magnetodynamic properties of Py100-xMx thin films (M=Pt, Ag, Au) and Py100-x-yPtxAgy thin films with different doping concentrations and the micro-scale spin Hall oscillator devices fabricated by the above thin films. The main results are as follows: 1. The magnetodynamic parameters of Py100-xMx alloy films (M = Pt, Ag, Au) doped with Py100-xMx as a function of doping concentration and doping elements. The magnetic static and dynamic properties of Py100-xMx films are studied systematically. The results show that: (1) the damping factors of Py100-xAgx or Py100-xAux films vary with doping concentration and doping elements. The Py_ 1oo_ xPtx thin films exhibit a quadratic square relationship with the increase of doping composition. Compared with the doping elements Ag and Au, Pt has the greatest influence on damping factor when Py doped into Pt. The damping factor of Py_ 70Pt_ 30 thin films is 4.5 times larger than that of pure Py single layer films. The damping factor of Py100-xAgx thin films is almost independent of the concentration of A g doped in Py100-xMx films; (2) The saturated magnetization of Py100-xMx thin films M shows a decreasing trend of quadratic element equation with the increase of doping concentration, the fastest decreasing trend is Au and the slowest decreasing trend is Pt; (3) The exchange stiffness coefficient A of Py100-xMx thin films decreases with the doping concentration. The experimental trend of the kinetic parameters coincides with the results calculated by DFT theory. The temperature dependence of the magnetic properties of Py100-xMx thin films with different doping metals and concentrations is studied by a temperature-dependent ferromagnetic resonance. It is found that the damping factor of Py100-xMx film increases with the increase of temperature, and Py70Au30 has the greatest increase. The spin wave constant D can be obtained by the frequency dependence of spin standing wave mode. The temperature dependence of D can be described by T2 law, showing the significant electron traveling characteristics in the film material. The spin-wave constant D was estimated by Bloch's law. The possible intrinsic excitation mechanism of Pyio0-xMx magnetic thin films was studied by comparing the two fitting methods. 2. Binary doped Py1oo-x-yPtxAgy thin films were characterized by defining three-dimensional parameter space and adjusting their MS, alpha and A independent variations in a certain range. Py100-x-yPtxAgy thin film system was successfully designed by adjusting the magnetic properties of permalloy. By adjusting the doping components of Pt and Ag, the saturated magnetization of Py100-x-yPtxAgy thin film with 100 nm thickness was kept unchanged and the damping factor was increased. Py100-x-yPtxAgy/Pt-SHNO device-single nano-compression structure. Py84Ag16/Pt (S01), Py77.5Pt10Ag12.5/Pt (S02), Py75Pt15Ag10/Pt (S03), Py73Pt198/Pt (S04) bilayer films were designed and fabricated on the basis of binary doped Py100-x-yPtxAgy thin films. The saturation magnetization of the films is 0 Meff = 0.617 (+ 0.034) T, and the damping factor is about 1-3 times as large as that of the films. On the basis of the above films, a single nano-compression SHNOs device with the same compression width of 150 nm has been successfully fabricated. Ne factor does not change the current-frequency dependence of the self-oscillation mode excited by the device; (2) After the self-oscillation behavior occurs, the peak width f becomes narrow sharply and tends to be stable with the increase of IDC. The minimum peak width f~9.6 MHz of the S01 device with low damping factor is smaller than that of the other devices with higher damping factor, and F is smaller. (3) The output power P of SHNOs devices increases exponentially with the increase of IDC, but decreases obviously with the increase of damping factor. (4) The critical current IDCth of self-oscillation increases linearly with the increase of damping factor. (5) Comparison and analysis of different applied magnetic fields and critical current IDCth. Under the same scanning current of 3.2mA, the constant current sweep magnetic field mu 0Hex, (1) the self-oscillation frequency increases with the increase of the applied magnetic field, which conforms to the relationship between the out-of-plane magnetic field and the oscillation frequency. As the saturation magnetization of the device is the same, the relationship between the peak frequency of self-oscillation and the variation of the applied magnetic field is basically the same. (2) The relationship between the output power P and the magnetic field of the SHNOs device is similar. First, the output power P increases with the increase of the applied magnetic field, reaches the peak value in the intermediate magnetic field, and finally decreases relatively until no self-oscillation is observed. Up to now, the maximum output power of SHNOs devices decreases monotonously with the increase of damping factor; (3) the minimum peak width decreases monotonously with the increase of damping factor. (4) Py100-x-yPtxAgy/Pt-SHNO devices-double nano-compression structures. On the basis of the same thin film structure and single nano-compression devices, double nano-particles were prepared. Squeezed SHNOs devices Py84Ag16/Pt (D01), Py77.5Pt10Ag12.5/Pt (D02), Py75Pt15Ag10/Pt (D03) and Py73Pt19Ag8/Pt (D04). The performance of SHNOs devices varies with scanning current. The peak width of the intersynchronous state of the SHNO device is much smaller than that of the unsynchronized state, and the output power of the intersynchronous state is larger than that of the two separate unsynchronized states. (2) When the distance between the two nanostructures is changed (dcc = 300 nm, 600 nm, 900 nm) The D01 device with low damping factor can observe the state of mutual synchronization at the spacing of 300 nm and 600 nm while the D02 device with slightly higher damping factor can only observe the state of mutual synchronization at the spacing of 300 nm. For D03 and D04, mutual synchronization is not observed at any spacing. Py84Ag16/Pt-SHNO device-multi-nano-compression structure.A series of five uniformly spaced nano-compression SHNO devices were fabricated on Py84Ag16/Pt bilayer film structure.The results were compared with those of Py84Ag16/Pt-SHNO device with double nano-compression structure.The nano-compression structures with the same width and spacing of 300 nm were obtained under the same magnetic field 6000 Oe. The maximum output power is more than twice as large, and the maximum output power is as high as 17 pW and the minimum peak width is less than 1 MHz under the magnetic field of 7000 Oe.
【學位授予單位】：東南大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：O484
【參考文獻】
相關期刊論文 前1條
1 楊軍;戴斌飛;李霞;;自旋軌道耦合效應及其應用研究[J];大學物理;2011年08期
，本文編號：2199721
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