NiFe/Pt薄膜中角度相关的逆自旋霍尔效应
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摘要
NiFe/Pt双层薄膜样品在铁磁共振时,NiFe磁矩进动所产生的自旋流注入到Pt层中,由于逆自旋霍尔效应产生直流电压VISHE,此电压会叠加到NiFe薄膜由于自旋整流效应而产生的电压VSRE上,实验测量所得电压为VISHE和VSRE的叠加.为了区分这两种不同机理对电压的贡献,本文采取旋转外加静磁场的方法,通过分析所测电压随磁场角度的变化从而分离出VISHE的大小.研究结果表明,相比于单层NiFe(20nm)薄膜样品,NiFe(20nm)/Pt(10nm)双层膜样品中由于NiFe自旋注入到Pt中导致铁磁共振线宽增加.与逆自旋霍尔效应产生的电压相比,自旋整流效应的贡献较小,但不可忽略.本文工作有助于认清铁磁/非磁性金属材料中的自旋相关效应,并提供了一种准确的分析逆自旋霍尔效应的方法.
In NiFe/Pt bilayer, when spin current originating from the magnetization procession of Ni Fe is inject into the adjacent Pt layer under ferromagnetic resonance(FMR), the direct current(DC) voltage VISHEgenerated by inverse spin Hall effect(ISHE) will be added to the voltage V_(SRE) generated by spin rectification effect(SRE), therefore the measured voltage in experiment is the sum of VISHEand V_(SRE) . It is crucial to separate these contributions, which has been often overlooked before, in order to make a reasonable comparison of the ISHE among different materials. The voltages having symmetric(Lorentz type) and anti-symmetric(dispersive type) components both vary with the static magnetic field strength. However, they have different static magnetic field angle dependences according to our theoretical analysis. In order to distinguish the contribution of ISHE from that of SRE, in this paper, we employ a method, in which the voltage across the sample is measured when the static magnetic field is applied to different directions, to analyze the voltage by varying magnetic field angle in a range from 0?to 360?in steps of 10?, thereby separating the VISHE. The separation is carried out by fitting the angle dependent symmetric and anti-symmetric curves to different theoretical formulas of ISHE and SRE. The voltages of the two different contributions together with the phase angle of the microwave are obtained.At the same time, the FMR line width and the resonant field can be read out. The results show that the ferromagnetic resonance line width in Ni Fe(20 nm)/Pt(10 nm) sample is larger than that in Ni Fe(20 nm) sample due to the injection of spin current from Ni Fe to Pt in the bi-layer sample. We notice that in the curves of voltage vs. static magnetic field,the Lorentz symmetry components of the voltage from the bi-layer sample weight more than those from the single-layer sample. This is explained as a result of the existence of the ISHE in the bi-layer sample, where the spins are pumped from the magnetic layer to the adjacent nonmagnetic layer. The spin pumping effect does not show up in the single-layer sample. There are a large portion of symmetric components in the double layer sample, which is attributed to the ISHE.Although the voltage caused by the SRE is smaller than that by the ISHE, the SRE voltage cannot be ignored. Our work is crucial to understanding the spin-related effects in ferromagnetic/nonmagnetic metal material and provides an improved analysis method to study the spin pumping and the ISHE.
In NiFe/Pt bilayer, when spin current originating from the magnetization procession of Ni Fe is inject into the adjacent Pt layer under ferromagnetic resonance(FMR), the direct current(DC) voltage VISHEgenerated by inverse spin Hall effect(ISHE) will be added to the voltage V_(SRE) generated by spin rectification effect(SRE), therefore the measured voltage in experiment is the sum of VISHEand V_(SRE) . It is crucial to separate these contributions, which has been often overlooked before, in order to make a reasonable comparison of the ISHE among different materials. The voltages having symmetric(Lorentz type) and anti-symmetric(dispersive type) components both vary with the static magnetic field strength. However, they have different static magnetic field angle dependences according to our theoretical analysis. In order to distinguish the contribution of ISHE from that of SRE, in this paper, we employ a method, in which the voltage across the sample is measured when the static magnetic field is applied to different directions, to analyze the voltage by varying magnetic field angle in a range from 0?to 360?in steps of 10?, thereby separating the VISHE. The separation is carried out by fitting the angle dependent symmetric and anti-symmetric curves to different theoretical formulas of ISHE and SRE. The voltages of the two different contributions together with the phase angle of the microwave are obtained.At the same time, the FMR line width and the resonant field can be read out. The results show that the ferromagnetic resonance line width in Ni Fe(20 nm)/Pt(10 nm) sample is larger than that in Ni Fe(20 nm) sample due to the injection of spin current from Ni Fe to Pt in the bi-layer sample. We notice that in the curves of voltage vs. static magnetic field,the Lorentz symmetry components of the voltage from the bi-layer sample weight more than those from the single-layer sample. This is explained as a result of the existence of the ISHE in the bi-layer sample, where the spins are pumped from the magnetic layer to the adjacent nonmagnetic layer. The spin pumping effect does not show up in the single-layer sample. There are a large portion of symmetric components in the double layer sample, which is attributed to the ISHE.Although the voltage caused by the SRE is smaller than that by the ISHE, the SRE voltage cannot be ignored. Our work is crucial to understanding the spin-related effects in ferromagnetic/nonmagnetic metal material and provides an improved analysis method to study the spin pumping and the ISHE.
引文
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[29]Kittel C 1947 Phys.Rev.71 270
[30]Chen L,Ikeda S,Matsukura F,Ohno H 2014 Appl.Phys.Express 7 013002
[31]Mosendz O,Pearson J E,Fradin F Y,Bauer G E W,Bader S E,Hoffmann A 2010 Phys.Rev.Lett.104046601
[2]Ando K,Takahashi S,Ieda J,Kajiwara Y,Nakayama H,Yoshino T,Harii K,Fujikawa Y,Matsuo M,Maekawa S,Saitoh E 2011 J.Appl.Phys.109 103913
[3]Kimura T,Otani Y,Sato T,Takahashi S,Maekawa S2007 Phys.Rev.Lett.98 156601
[4]Wang R X,He P B,Xiao Y C,Li J Y 2015 Acta Phys.Sin.64 137201(in Chinese)[王日兴,贺鹏斌,肖运昌,李建英2015物理学报64 137201]
[5]Tserkovnyak Y,Brataas A,Bauer G E W 2002 Phys.Rev.Lett.88 117601
[6]Saitoh E,Ueda M,Miyajima H,Tatara G 2006 Appl.Phys.Lett.88 182509
[7]Slachter A,Bakker F L,Adam J P,van Wees B J 2010Nat.Phys.6 879
[8]Adachi H,Uchida K,Saitoh E,Maekawa S 2013 Rep.Prog.Phys.76 036501
[9]Wu H,Wan C H,Yuan Z H,Zhang X,Jiang J,Zhang Q T,Wen Z C,Han X F 2015 Phys.Rev.B 92 04404
[10]Ando K,Morikawa M,Trypiniotis T,Fujikawa Y,Barnes C H W,Saitoh E 2010 Appl.Phys.Lett.96082502
[11]Wu Y,Zhao Y L,Xiong Q,Xu X G,Sun Y,Zhang S Q,Jiang Y 2014 Chin.Phys.B 23 018503
[12]Gong S J,Duan C G 2015 Acta Phys.Sin.64 187103(in Chinese)[龚士静,段纯刚2015物理学报64 187103]
[13]Hoffmann A 2013 IEEE Trans.Magn.49 5172
[14]Hahn C,De Loubens G,Viret M,Klein O,Naletov V V,Youssef J B 2013 Phys.Rev.Lett.111 217204
[15]Jungfleisch M B,Chumak A V,Kehlberger A,Lauer V,Kim D H,Onbasli M C,Ross C A,Kl?ui M,Hillebrands B 2015 Phys.Rev.B 91 134407
[16]Zhang W,Jungfleisch M B,Jiang W J,Sklenar J,Fradin F Y,Pearson J E,Ketterson J B,Hoffmann A 2015 J.Appl.Phys.117 172610
[17]Nan T X,Emori S,Boone C T,Wang X J,Oxholm T M,Jones J G,Howe B M,Brown G J,Sun N X 2015Phys.Rev.B 91 214416
[18]Deorani P,Yang H 2013 Appl.Phys.Lett.103 232408
[19]Shikoh E,Ando K,Kubo K,Saitoh E,Shinjo T,Shiraishi M 2013 Phys.Rev.Lett.110 127201
[20]Dushenko S,Koike M,Ando Y,Shinjo T,Myronov M,Shiraishi M 2015 Phys.Rev.Lett.114 196602
[21]Ando K,Saitoh E 2012 Nat.Commun.3 629
[22]Ando Y,Ichiba K,Yamada S,Shikoh E,Shinjo T,Hamaya K,Shiraishi M 2013 Phys.Rev.B 88 140406
[23]Feng Z,Hu J,Sun L,You B,Wu D,Du J,Zhang W,Hu A,Yang Y,Tang D M,Zhang B S,Ding H F 2012Phys.Rev.B 85 214423
[24]Liu L Q,Pai C F,Li Y,Tseng H W,Ralph D C,Buhrman R A 2012 Science 336 555
[25]Mukherjee S S,Deorani P,Kwon J H,Yang H 2012 Phys.Rev.B 85 094416
[26]Soh W T,Peng B,Chai G Z,Ong C K 2014 Rev.Sci.Instrum.85 026109
[27]Soh W T,Peng B,Ong C K 2014 J.Phys.D:Appl.Phys.47 285001
[28]Gui Y S,Bai L H,Hu C M 2013 Sci.China 56 124
[29]Kittel C 1947 Phys.Rev.71 270
[30]Chen L,Ikeda S,Matsukura F,Ohno H 2014 Appl.Phys.Express 7 013002
[31]Mosendz O,Pearson J E,Fradin F Y,Bauer G E W,Bader S E,Hoffmann A 2010 Phys.Rev.Lett.104046601