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The inverse spin Hall effect (ISHE), namely spin flows converted into charge currents due to spin orbital interaction, is investigated extensively in heavy metals, such as Pt, W, Au, etc. Recently, the effect was also found in Cu doped with Au. Their difference is that the spin Hall effect is from the intrinsic effect which is related to the topological character of the electronic bands, while the ISHE is mainly from the extrinsic spin dependent scattering by the impurities. The impurity scattering can give opportunities to tune the effect, for example by impurity concentration, which is impossible by the intrinsic mechanism. In this work, we extend the material to the doped oxides. NiFe films are deposited on undoped and doped SrTiO3 substrates by magnetron sputtering, respectively. The spins are injected from the magnetic thin films by spin pumping through using a shorted microstrip transmission line fixture at different frequencies and room temperature. The spin rectification voltage and the inverse spin Hall voltage in the doped sample are separated by the inverting spin injection direction method, which is realized by flipping the samples. The results show that in the undoped SrTiO3 substrate, the voltage curves before and after flipping the sample are basically the same, which is due to the voltage generated by the spin rectification effect of the NiFe film. For Nb-doped SrTiO3 substrates with Nb concentration x = 0.028, 0.05, 0.1, 0.15 and 0.2, the inverse spin Hall voltage decreases with doping concentration increasing and is not detectable in sample with doping concentration of 0.15, nor with doping concentration of 0.2. The decrease of the ISHE effect may be due to the spin coherent length decreasing with the increase of the impurity concentration. The correlation between spin-charge conversion and transportation needs knowing in detail. Nevertheless, the results show that by doping strong spin-orbit coupling impurities into SrTiO3, thus by changing the doping concentration, the inverse spin Hall effect in SrTiO3 can be controlled. This tunable spin-charge conversion provides more possibilities for developing the spintronic devices and it will have great potential applications in the future.
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Keywords:
- doping /
- SrTiO3 /
- inverse spin Hall effect
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图 1 测试平台原理图
Figure 1. Schematic diagram of the test platform
图 2 NiFe/STO在不同频率下的测试曲线(a)及4.4 GHz时的翻转测试曲线(b)
Figure 2. Voltages of NiFe/STO at different frequencies(a) and reversal test curves at 4.4 GHz before and after sample flip(b)
图 3 NiFe/STO中铁磁共振线宽ΔH随频率f的变化曲线(a)和频率f随铁磁共振场Hr的变化曲线(b)
Figure 3. Linewidth (ΔH) of ferromagnetic resonance varies with frequency f (a) and frequency f varies with resonance field(Hr) (b) in NiFe/STO
图 4 NiFe/0.05Nb:STO体系3.4 GHz时的测试曲线, 插图为该体系3.4 GHz时的VSRE和VISHE随外磁场的变化曲线
Figure 4. Test curve at 3.4GHz in NiFe/0.05Nb:STO, the inset shows the variation of VSRE and VISHE with external magnetic field at 3.4 GHz
图 5 3.4 GHz时不同掺杂浓度的VISHE随外磁场的变化曲线
Figure 5. Variation curve of VISHE with different doping concentrations with external magnetic field at 3.4 GHz
图 6 各掺杂浓度样品频率f与线宽ΔH的拟合曲线, 插图为阻尼系数α与掺杂浓度的关系
Figure 6. Fitting curves of frequency f and linewidth ΔH at different doping concentrations,the inset shows the relationship between the damping coefficient α and the doping concentration
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[1] Valenzuela S O, Tinkham M 2006 Nature 442 176
Google Scholar
[2] Kimura T, Otani Y, Sato T, Takahashi S, Maekawa S 2007 Phys. Rev. Lett. 98 156601
Google Scholar
[3] Liu L, Pai C F, Li Y, Tseng H W, Ralph D C, Buhrman R A 2012 Science 336 555
Google Scholar
[4] Kato Y K, Myers R C, Gossard A C, Awschalom D D 2004 Science 306 1910
Google Scholar
[5] Kumar A, Bansal R, Chaudhary S, Muduli P K 2018 Phys. Rev. B 98 104403
Google Scholar
[6] Nakayama H, Ando K, Harii K, Fujikawa Y, Kajiwara Y, Yoshino T, Saitoh E 2010 IEEE Trans. Magn. 46 2202
Google Scholar
[7] Jungwirth T, Qian N, Macdonald A H 2002 Phys. Rev. Lett. 88 207208
Google Scholar
[8] Guo G Y, Murakami S, Chen T W, Nagaosa N 2008 Phys. Rev. Lett. 100 096401
Google Scholar
[9] Bottegoni F, Ferrari A, Cecchi S, Finazzi M, Ciccacci F, Isella G 2013 Appl. Phys. Lett. 10215241 1
[10] Ramaswamy R, Wang Y, Elyasi M, Motapothula M, Venkatesan T, Qiu X, Yang H 2017 Phys. Rev. Appl. 8 024034
Google Scholar
[11] Tse W K, Das S S 2006 Phys. Rev. Lett. 96 056601
Google Scholar
[12] Fert A, Levy P M 2011 Phys. Rev. Lett. 106 157208
Google Scholar
[13] Gradhand M, Fedorov D V, Zahn P, Mertig I 2010 Phys. Rev. Lett. 104 186403
Google Scholar
[14] Choi W Y, Kim H J, Chang J, Han S H, Abbout A, Saidaoui H B M, Manchon A, Lee K J, Koo H C 2018 Nano Lett. 18 7998
Google Scholar
[15] Zhang W, Peng B, Han F, Wang Q, Soh W T, Ong C K, Zhang W 2016 Appl. Phys. Lett. 108 102405
Google Scholar
[16] Wang Q, Zhang W, Peng B, Zhang W 2017 Aip. Adv. 7 125218
Google Scholar
[17] Mosendz O, Vlaminck V, Pearson J E, Fradin F Y, Bauer G E W, Bader S D, Hoffmann A 2010 Phys. Rev. B 82 214403
Google Scholar
[18] Ando K, Takahashi S, Ieda J, Kajiwara Y, Saitoh E 2011 J. Appl. Phys. 109 103913
Google Scholar
[19] Deorani P, Yang H 2013 Appl. Phys. Lett. 103 232408
Google Scholar
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