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采用磁控溅射法在未掺杂和掺杂的SrTiO3基片上沉积了NiFe薄膜, 通过翻转测试法分离出掺杂样品中的自旋整流电压和逆自旋霍尔电压. 研究结果表明: 在未掺杂的SrTiO3基片中, 翻转前后测试的电压曲线基本一致, 为NiFe薄膜自旋整流效应产生的电压. 对于掺Nb浓度x为0.028, 0.05, 0.1, 0.15, 0.2的SrTiO3基片, 分离出的逆自旋霍尔电压随掺杂浓度增加而减小, 在掺杂浓度为0.15和0.2的样品中没有探测到明显的逆自旋霍尔电压. 本文的结果表明, 在SrTiO3中掺入强自旋轨道耦合的杂质, 通过掺杂浓度可以实现对SrTiO3中逆自旋霍尔效应的调控, 这类可调控的自旋相关研究为自旋电子器件的研究和开发提供了更多的可能性, 具有很大的潜在应用价值.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 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)
Fig. 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)
Fig. 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
Fig. 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
Fig. 5. Variation curve of VISHE with different doping concentrations with external magnetic field at 3.4 GHz
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[1] Valenzuela S O, Tinkham M 2006 Nature 442 176
Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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Google Scholar
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