磁性薄膜的L-S耦合研究
发布时间：2018-08-23 19:42
【摘要】：坡莫合金Py(Py=Ni80Fe20)作为重要的软磁材料,具有低矫顽力、低磁各向异性、低阻尼因子等特点,广泛的应用于自旋电子学的研究中。而过渡重金属元素铂(Pt),银(Ag),金(Au)具有较大的自旋轨道(L-S)耦合作用,可以通过与Py的掺杂,修饰或影响自旋电子学器件的磁学性质。因此,本论文以坡莫合金-重金属掺杂薄膜为主要研究对象,系统地研究了不同掺杂浓度的Py100-xMx薄膜(M = Pt,Ag,Au)和Py100-x-yPtxAgy薄膜的磁动力学性质的调控以及采用以上薄膜制备的自旋霍尔振荡器件的微波传输性质。主要研究结果包括以下几个方面:1.一元掺杂Py100-xMx合金薄膜(M = Pt, Ag, Au)的磁动力学参数随掺杂浓度和掺杂元素的变化。系统研究了 Py100-xMx薄膜的磁静态、动态性质,研究发现:(1)Py100-xAgx或Py100-xAux系列薄膜的阻尼因子随着掺杂组分的增加而呈现出线性增强趋势,而Py1oo-xPtx系列薄膜呈现出一个二次平方的关系行为。和掺杂元素Ag和Au相比,当Py掺杂进Pt时,Pt对阻尼因子有最大的影响,Py70Pt30薄膜的阻尼因子α =0.035是纯Py单层薄膜阻尼因子的4.5倍大。另一方面,Py100-xAgx薄膜的阻尼因子几乎和掺杂的Ag浓度变化不相关;(2)Py100-xMx薄膜的饱和磁化强度Ms随着掺杂浓度的增加而显示了一个二次元方程的递减关系趋势,减小最快的是Au而减少最慢的是Pt; (3)Py100-xMx薄膜的交换劲度系数A随着掺杂浓度的增加而呈现出线性递减的趋势,其中Py100-xAgx和Py100-xAux薄膜的A下降的相对较快。该动力学参数的实验趋势与DFT理论计算的结果一致符合。通过变温铁磁共振仪研究了不同掺杂金属及浓度对Py100-xMx薄膜磁性的温度依赖关系的变化影响。实验发现Py100-xMx薄膜的阻尼因子随着温度的增加而增加,其中Py70Au30的增幅最大。通过自旋驻波模式的频率依赖性能够得到自旋波常数D, D的温度依赖性能够通过T2定律描述,显示了薄膜材料中显著的电子的巡游特性。同时对Ms的温度依赖性进行了测量和拟合,并通过Bloch定律估算了自旋波常数D,比较两种拟合方法研究了 Pyio0-xMx磁性薄膜的可能内在激发机制。2.二元掺杂Py1oo-x-yPtxAgy薄膜,定义三维的参数空间,在一定的范围内调控其MS,α和A独立变化。为了独立调控坡莫合金的磁性,成功设计了合金薄膜系统Py100-x-yPtxAgy,通过调制Pt和Ag的掺杂组分,保持饱和磁化强度MS不变,提高阻尼因子的设想。成功的制备了厚度为100 nm的Py100-x-yPtxAgy薄膜,实现了平均饱和磁化强度保持为μ0MS=0.724± 0.014 T,而阻尼因子随着Pt组分的增加而有接近4倍的增长。3. Py100-x-yPtxAgy/Pt - SHNO器件-单纳米压缩结构。以二元掺杂的Py100-x-yPtxAgy薄膜为基础,设计和制备了 Py84Ag16/Pt(S01),Py77.5Pt10Ag12.5/Pt (S02), Py75Pt15Ag10/Pt (S03),Py73Pt19Ag8/Pt (S04)双层薄膜,该系列薄膜的饱和磁化强度μ0Meff = (0.617±0.034) T,阻尼因子的可调控范围为1-3倍左右。在上述薄膜基础上,成功的制备了单纳米压缩结构的SHNOs器件,压缩结构具有相同宽度150nm。研究发现,在同一磁场0.5T下,固定磁场扫电流IDC,(1)不断增加的阻尼因子不会改变器件所激发自振荡模式的电流-频率依赖关系;(2)在自振荡行为发生之后,峰宽Δf急剧变窄,且随着IDC的不断增加而趋于平稳状态。低阻尼因子S01器件的最小峰宽Δf～ 9.6 MHz,而其他较高阻尼因子器件具有更小的峰宽,Δf～ 3 MHz; (3) SHNOs器件的输出功率P均随着IDC的增加而以指数的形式增加,但是随着器件阻尼因子的增大,P出现了明显的下降;(4)自振荡发生的临界电流IDCth几乎随着阻尼因子的增大而线性增加。(5)对比分析不同外加磁场与临界电流IDCth在的变化关系,SHNO器件的阻尼因子越小而在越高的外加磁场下,越有利于器件保持激发自振荡状态。在同一扫描电流3.2mA下,固定电流扫磁场μ0Hex,(1)自振荡频率随着外加磁场的增加而不断增加,符合面外磁场与振荡频率的关系规律,且由于器件的饱和磁化强度均相同,自振荡峰频率与外加扫描磁场的变化关系基本一致;(2) SHNOs器件的输出功率P与磁场的变化关系相似,首先随着外加磁场的增加而增大,在中间磁场时达到峰值,最后相对下降,直到没有自振荡被观测到为止。SHNOs器件产生的最大输出功率随着阻尼因子的增大而单调递减;(3)最小峰宽随着增加的阻尼因子也呈现单调递减的趋势。4. Py100-x-yPtxAgy/Pt - SHNO器件-双纳米压缩结构。在相同的薄膜结构和单纳米压缩器件的基础上,制备了双纳米压缩结构的SHNOs 器件 Py84Ag16/Pt(D01),Py77.5Pt10Ag12.5/Pt(D02),Py75Pt15Ag10/Pt(D03),Py73Pt19Ag8/Pt(D04)。研究了 SHNOs器件的性能随着扫描电流的变化。在同一磁场下,(1)当固定SHNOs器件的双纳米压缩结构间隔(dcc = 300 nm)时,随着阻尼因子的不断增加,互同步性减弱或消失,输出功率减弱,峰宽增大。SHNO器件的互同步状态的峰宽不但比未同步态的要小很多,而且互同步状态的输出功率要比两个单独未同步态下的输出功率之和还要大;(2)当改变双纳米压缩结构的间距(dcc= 300nm,600nm,900nm)来观察SHNOs器件的互同步状态变化时,低阻尼因子的D01器件能够在间距为300 nm和600 nm的情况下观察到互同步状态,而稍高阻尼因子的D02器件只能在间距为300 nm的情况下观测到互同步状态,对器件D03和D04来说,未在任何间距下观测到互同步状态。5.Py84Ag16/Pt-SHNO器件-多纳米压缩结构。在Py84Ag16/Pt的双层膜结构上制备一列5个等间距纳米压缩结构的SHNO器件,与双纳米压缩结构的Py84Ag16/Pt-SHNO器件结果对比,同一磁场6000 Oe下,相同宽度的纳米压缩结构,间距也同为300 nm时,得到的最大输出功率要大2倍多;并且在磁场为7000 Oe下,最大输出功率高达17pW,最小峰宽小于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.
【学位授予单位】：东南大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O484
本文编号：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.
【学位授予单位】：东南大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O484
【参考文献】
相关期刊论文 前1条
1 杨军;戴斌飞;李霞;;自旋轨道耦合效应及其应用研究[J];大学物理;2011年08期
，本文编号：2199721
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