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GeTe基稀磁半导体材料因具有可独立调控载流子浓度和磁性离子浓度的特性而受到广泛关注. 本文利用脉冲激光沉积技术制备了该体系的单晶外延薄膜, 并通过高价态Bi元素部分取代Ge元素的方法实现了材料中载流子类型从空穴向电子的转变, 即制备出N型GeTe基稀磁半导体. 测量结果表明, 无论是室温还是低温下的Hall电阻曲线皆呈现负斜率, 说明体系中载流子是电子; 并且当Bi掺杂量达到32%时, 电子浓度为1021/cm3. 变温输运性质的测量证明体系的输运行为呈现半导体特征. 通过测量低温10 K下的绝热磁化曲线, 在高Bi掺杂体系中观测到了明显的铁磁行为, 而低于32%Bi掺杂量的体系中未观察到. 这一结果说明, 高掺杂Bi的替代导致载流子浓度的增加, 促进了载流子传递Ruderman-Kittel-Kasuya-Yoshida相互作用, 使得分散的Fe-Fe之间产生磁耦合作用, 进而形成铁磁有序态.
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关键词:
- 稀磁半导体 /
- 外延薄膜 /
- Ruderman-Kittel-Kasuya-Yoshida相互作用 /
- 铁磁有序态
The epitaxial thin films of Ge0.96−xBixFe0.04Te are deposited on BaF2 substrates by using pulsed laser deposition technique. The thin films with three different compositions i.e. Ge0.8Bi0.2Te, Ge0.76Bi0.2Fe0.04Te, and Ge0.64Bi0.32Fe0.04Te are prepared in this wok. Their high-quality epitaxy and crystallinity are confirmed by X-ray diffraction and atomic force microscopy. According to the measurements of Hall effect variation, we find that each of all curves exhibits a negative slope for the different films as the temperature varies from low temperature to room temperature, indicating that Ge0.96−xBixFe0.04Te films are n-type material because the substitution of Bi for Ge makes the carriers change from holes into electrons. Temperature dependence of resistivity confirms that the electronic transport behavior for each of Ge0.96−xBixFe0.04Te thin films exhibits a typical semiconductor characteristic. From the measurements of temperature dependence of electronic transport under various external magnetic fields, we find that the Ge0.64Bi0.32Fe0.04Te thin film shows some magnetoresistive effect while other composition films do not possess such a property. Based on the linear fitting of temperature dependence of magnetic susceptibility in high temperature and low temperature region, the magnetic property of Ge0.64Bi0.32Fe0.04Te thin film changes from 253 K. Together with the study of magnetic susceptibility curve in the paramagnetic region, the Curie-Weiss temperature is determined to be 102 K. At a low temperature of 10.0 K, we observe an obvious ferromagnetic hystersis loop in Ge0.64Bi0.32Fe0.04Te instead of in Ge0.76Bi0.2Fe0.04Te thin film. These results imply that the increase of Bi dopant is main reason for the establishment of ferromagnetic ordering state. The carrier concentration increases and thus promotes the carriers transporting the Ruderman-Kittel-Kasuya-Yoshida interaction, thereby leading to the separated Fe ions producing the magnetic interaction and forming an n-type diluted magnetic semiconductor.-
Keywords:
- diluted magnetic semiconductor /
- epitaxial thin film /
- Ruderman-Kittel-Kasuya-Yoshida interaction /
- ferromagnetic state
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图 3 (a) Ge0.76Bi0.2Fe0.04Te薄膜不同温度下霍尔效应测量结果, 插图为载流子浓度随温度变化; (b) Ge0.64Bi0.32Fe0.04Te薄膜不同温度下霍尔效应测量结果, 插图为载流子浓度随温度变化
Fig. 3. (a) Magnetic field dependence of Hall voltage for Ge0.76Bi0.2Fe0.04Te film under different temperatures, inset shows the temperature dependence of carrier concentrations; (b) magnetic field dependence of Hall voltage for Ge0.64Bi0.32Fe0.04Te film under different temperatures, inset shows the temperature dependence of carrier concentrations.
图 4 (a) Ge0.76Bi0.2Fe0.04Te和Ge0.64Bi0.32Fe0.04Te电阻率随温度变化曲线; (b)迁移率随温度变化曲线; (c) Ge0.76Bi0.2Fe0.04Te薄膜在零磁场和3.0 T磁场下变温电阻率曲线; (d) Ge0.64Bi0.32Fe0.04Te薄膜在零磁场和3.0 T磁场下变温电阻率曲线
Fig. 4. (a) Temperature dependent resistivity of Ge0.76Bi0.2Fe0.04Te and Ge0.64Bi0.32Fe0.04Te film; (b) temperature dependent resistivity of mobility; (c) temperature dependent resistivity of Ge0.76Bi0.2Fe0.04Te film under 0 T and 3.0 T field; (d) emperature dependent resistivity of Ge0.64Bi0.32Fe0.04Te film under 0 T and 3.0 T field.
图 5 Ge0.64Bi0.32Fe0.04Te薄膜磁化率随温度变化曲线; 插图为磁化率倒数随温度变化曲线, 直线是利用居里外斯定律拟合的结果
Fig. 5. Temperature dependence of magnetic susceptibility curves for Ge0.64Bi0.32Fe0.04Te film; inset shows temperature dependence of inverse magnetic susceptibility and the solid line is the fitting result with the Cuire-Weiss law.
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[1] Ohno H, Chiba D, Matsukura F, Omiya T, Abe E, Dietl T, Ohno Y, Ohtani K 2000 Nature 408 944
Google Scholar
[2] Burch K, Shrekenhamer D, Singley E, Stephens J, Sheu B, Kawakami R, Schiffer P, Samarth N, Awschalom D, Basov D 2006 Phys. Rev. Lett. 97 087208
Google Scholar
[3] Richardella A, Roushan P, Mack S, Zhou B, Huse D, Awschalom D, Yazdani A 2010 Science 327 665
Google Scholar
[4] Li Y Y, Cao Y F, Wei G N, Li Y Y, Ji Y, Wang K Y, Edmonds K W, Rushforth A W, Foxon C T, Gallagher B L 2013 Appl. Phys. Lett. 103 022401
Google Scholar
[5] Prinz G A 1998 Science 282 1660
Google Scholar
[6] Pappert K, Humpfner S, Gould C, Wenisch J, Brunner K, Schmidt G, Molenkamp L W 2007 Nat. Phys. 3 573
Google Scholar
[7] Wang K Y, Edmonds K W, Irvine A C, Tatara G, de Ranieri E, Wunderlich J, Olejnik K, Rushforth A W, Campion R P, Williams D A, Foxon C T, Gallagher B L 2010 Appl. Phys. Lett. 97 262102
Google Scholar
[8] Fan J Y, Eom J H 2008 Appl. Phys. Lett. 92 142101
Google Scholar
[9] Yang M Y, Cai K M, Ju H L, Edmonds K W, Yang G, Liu S, Li B H, Zhang B, Sheng Y, Wang S G, Ji Y, Wang K Y 2016 Sci. Rep. 6 20778
Google Scholar
[10] Cai K M, Yang M Y, Ju H L, Wang S M, Ji Y, Li B H, Edmonds K W, Sheng Y, Zhang B, Zhang N, Liu S, Zheng H Z, Wang K Y 2017 Nat. Mat. 16 712
Google Scholar
[11] Kolobov A V, Tominaga J 2003 Appl. Phys. Lett. 82 382
Google Scholar
[12] Lee S H, Ko D K, Jung Y, Agarwal R 2006 Appl. Phys. Lett. 89 223116
Google Scholar
[13] Akola J, Jones R O 2007 Phys. Rev. B 76 235201
Google Scholar
[14] Sante D D, Barone P, Bertacco R, Picozzi S 2013 Adv. Mater. 25 509
Google Scholar
[15] 张楠, 张保, 杨美音, 蔡凯明, 盛宇, 李予才, 邓永城, 王开友 2017 物理学报 66 027501
Google Scholar
Zhang N, Zhang B, Yang M Y, Cai K M, Sheng Y, Li Y C, Deng Y C, Wang K Y 2017 Acta Phys. Sin. 66 027501
Google Scholar
[16] 杜成旭, 王婷, 杜颖妍, 贾倩, 崔玉亭, 胡爱元, 熊元强, 毋志民 2018 物理学报 67 187101
Google Scholar
Du C X, Wang T, Du Y Y, Jia Q, Cui Y T, Hu A Y, Xiong Y Q, Wu Z M 2018 Acta Phys. Sin. 67 187101
Google Scholar
[17] Jantsch W 1983 Dielectric Properties and Soft Modes in Semiconducting (Pb, Sn, Ge)Te, Springer Tracts in Modern Physics Vol. 99 (Berlin: Springer Verlag)
[18] Fukuma Y, Asada H, Miyawaki S, Koyanagi T, Senba S, Goto K, Sato H 2008 Appl. Phys. Lett. 93 252502
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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
[24] Chen L L, Fan J Y, Tong W, Hu D Z, Du H F, Zhang L, Ling L S, Pi L, Zhang Y H, Yang H 2018 J. Mater. Sci. 53 323
Google Scholar
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