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Many emergent and novel phenomena occur in nonmagnetic/ferromagnet heterostructures. In particular, Pt/ferromagnet heterostructures where the Pt has strong spin-orbit coupling and thus can convert spin current into charge current, has attracted a great attention recently. The anomalous Hall effect (AHE) has been found in many Pt/ferromagnet heterostructures. However, the underlying physics remains elusive, so it is necessary to find more heterostructures in order to provide more experimental data. In this work, we investigate anomalous Hall resistances (AHRs) in Pt thin films sputtered on epitaxial La0.67Sr0.33MnO3 (LSMO) ferromagnetic films. High-quality Pt/LSMO heterojunctions are fabricated by pulsed laser deposition and RF-magnetron sputtering. The physical properties of LSMO films are characterized by the measurements of magnetic and transport properties. The AHR mainly contributed by Pt in the Pt/LSMO heterojunction increases sharply with temperature decreasing and changes its sign below 40 K. Furthermore, the AHR decreases sharply with the increase of Pt thickness. Those facts suggest that the ferromagnetism of Pt originates from interface due to magnetic proximity effect. Interestingly, this heterojunction can exhibit possible signal of topological Hall effect under low applied magnetic field. The above results provide an experimental basis for further understanding the interactions between electron spin and charge transport in nonmagnetic/ferromagnetic heterostructures.
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Keywords:
- anomalous Hall effect /
- magnetic proximity effect /
- topological Hall effect /
- epitaxial growth
[1] Ohno Y, Young D K, Beschoten B, Matsukura F, Ohno H, Awschalom D D 1999 Nature 402 790Google Scholar
[2] Jedema F J, Filip A T, Wees B J V 2001 Nature 410 345Google Scholar
[3] Heinrich B, Tserkovnyak Y, Woltersdorf G, Brataas A, Urban R, Bauer G E W 2003 Phys. Rev. Lett. 90 187601Google Scholar
[4] Kajiwara Y, Harii K, Takahashi S, Ohe J, Uchida K, Mizuguchi M, Umezawa H, Kawai H, Ando K, Takanashi K, Maekawa S, Saitoh E 2010 Nature 464 262Google Scholar
[5] Heinrich B, Burrowes C, Montoya E, Kardasz B, Girt E, Song Y Y, Sun Y Y, Wu M Z 2011 Phys. Rev. Lett. 107 066604Google Scholar
[6] Rezende S M, Rodriguez S R L, Soares M M, Vilela L L H, Ley D D, Azevedo A 2013 Appl. Phys. Lett. 102 012402Google Scholar
[7] Uchida K, Takahashi S, Harii K, Ieda J, Koshibae W, Ando K, Maekawa S, Saitoh E 2008 Nature 455 778Google Scholar
[8] Uchida K, Xiao J, Adachi H, Ohe J, Takahashi S, Ieda J, Ota T, Kajiwara Y, Umezawa H, Kawai H, Bauer G E W, Maekawa S, Saitoh E 2010 Nat. Mater. 9 894Google Scholar
[9] Weng H M, Yu R, Hu X, Dai X, Fang Z 2015 Adv. Phys. 64 03227Google Scholar
[10] Takahashi S, Maekawa S 2008 Sci. Technol. Adv. Mater. 9 014105Google Scholar
[11] Miao B F, Huang S Y, Qu D, Chien C L 2014 Phys. Rev. Lett. 112 236601Google Scholar
[12] Althammer M, Meyer S, Nakayama H, Schreier M, Altmannshofer S, Weiler M, Huebl H, Geprags S, Opel M, Gross R, Meier D, Klewe C, Kuschel T, Schmalhorst J M, Reiss G, Shen L M, Gupta A, Chen Y T, Bauer G E W, Saitoh E, Goennenwein S T B 2013 Phys. Rev. B 87 224401Google Scholar
[13] Lu Y M, Choi Y, Ortega C M, Cheng X M, Cai J W, Huang S Y, Sun L, Chien C L 2013 Phys. Rev. Lett. 110 147207Google Scholar
[14] Isasa M, Pinto A B, Velez S, Golmar F, Sanchez F, Hueso L E, Fontcuberta J, Casanova F 2014 Appl. Phys. Lett. 105 142402Google Scholar
[15] Shang T, Zhan Q F, Yang H L, Zuo Z H, Xie Y L, Zhang Y, Liu L P, Wang B M, Wu Y H, Zhang S, Li R W 2015 Phys. Rev. B 92 165114Google Scholar
[16] Liao Z L, Li F M, Gao P, Li L, Guo J D, Pan X Q, Jin R, Plummer E W, Zhang J D 2015 Phys. Rev. B 92 125123Google Scholar
[17] Uchida K, Qiu Z Y, Kikkawa T, Lguchi R L, Saitoh E 2015 Appl. Phys. Lett. 106 052405Google Scholar
[18] Putter S, Geprags S, Schlitz R, Althammer M, Erb A, Gross R, Goennenwein S T B 2017 Appl. Phys. Lett. 110 012403Google Scholar
[19] Biswas A, Yang C H, Ramesh R, Jeong M H 2017 Prog. Surf. Sci. 92 02117Google Scholar
[20] Peng R, Xu H C, Xia M, Zhao J F, Xie X, Xu D F, Xie B P, Feng D L 2014 Appl. Phys. Lett. 104 081606Google Scholar
[21] Snyder G J, Hiskes R, DiCarolis S, Beasley M R, Geballe T H 1996 Phys. Rev. B 53 14434Google Scholar
[22] Huang S Y, Fan X, Qu D, Chen Y P, Wang W G, Wu J, Chen T Y, Xiao J Q, Chien C L 2012 Phys. Rev. Lett. 109 107204Google Scholar
[23] Soumyanarayanan A, Raju M, Oyarce A L G, Tan A K C, Im M Y, Petrovi A P, Ho P, Khoo K H, Tran M, Gan C K, Ernult F, Panagopoulos C 2017 Nat. Mater. 16 898Google Scholar
[24] Zhang S, Zhang S S L 2009 Phys. Rev. Lett. 102 086601Google Scholar
[25] Li Y, Kanazawa N, Yu X Z, Tsukazaki A, Kawasaki M, Ichikawa M, Jin X F, Kagawa F, Tokura Y 2013 Phys. Rev. Lett. 110 117202Google Scholar
[26] Belabbes A, Bihlmayer G, Bechstedt F, Blügel S, Manchon A 2016 Phys. Rev. Lett. 117 247202Google Scholar
[27] Meng K K, Zhao X P, Liu P F, Liu Q, Wu Y, Li Z P, Chen J K, Miao J, Xu X G, Zhao J H, Jiang Y 2018 Phys. Rev. B 97 060407Google Scholar
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图 2 形貌表征 (a) STO (001)衬底AFM图; (b) LSMO (40 u.c.)薄膜AFM图; (c) Pt(2 nm)/LSMO(40 u.c.)薄膜AFM图; (d)和(e)分别为(b)和(c)中薄膜表面线扫描图
Figure 2. Morphology characterization: (a) AFM image of STO (001) substrate; (b) AFM image of LSMO (40 u.c.) film; (c) AFM image of Pt(2 nm)/LSMO(40 u.c.) film; (d) line-scan of the LSMO film in (b); (e) line-scan of the Pt/LSMO film in (c).
图 3 结构表征 (a) Pt(6 nm)/LSMO(40 u.c.)薄膜的2θ-ω扫描; (b)为(a)中(002)衍射峰的放大图, 插图为LSMO薄膜(002)衍射峰的摇摆曲线; (c) Pt/LSMO薄膜在(103)衍射峰附近的倒易空间图; (d) Pt/LSMO薄膜的XRR谱, 拟合的红线与实验数据相符
Figure 3. Structure characterization: (a) 2θ-ω scan of Pt(6 nm)/LSMO(40 u.c.) thin films; (b) enlarged view of the (002) diffraction peak in panel (a), and the inset is a rocking curve of LSMO film around (002) diffraction peak; (c) reciprocal space map of Pt/ LSMO film around (103) diffraction peak; (d) XRR spectrum of Pt/LSMO film, and the red line is a fit to the experimental data
图 4 (a) LSMO (40 u.c.)薄膜的磁化强度的温度依赖性, 插图为磁化强度对温度的一阶微分; (b) LSMO (40 u.c.)薄膜不同温度下的磁化强度的场依赖性, 插图为3 K时曲线的中心放大图
Figure 4. (a) Temperature dependence of magnetization of LSMO (40 u.c.) films, the inset is the first derivative of magnetization versus temperature; (b) field dependence of the magnetization of LSMO (40 u.c.) films at different temperatures, and the inset is an enlarged view of the curve at 3 K.
图 7 (a) 在2 K时不同Pt厚度的Pt/LSMO(40 u.c.)薄膜的RAHR, 其中4和6 nm曲线的RAHR分别扩大了4倍和5倍; (b) Pt(6 nm)/LSMO(40 u.c.)薄膜在不同温度下的RAHR
Figure 7. (a) RAHR of Pt/LSMO(40 u.c.) film with different Pt thickness, which were measured at 2 K. RAHR of the 4 and 6 nm curves are enlarged by a factor of four and five, respectively; (b) RAHR of Pt(6 nm)/LSMO(40 u.c.) films at different temperatures.
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[1] Ohno Y, Young D K, Beschoten B, Matsukura F, Ohno H, Awschalom D D 1999 Nature 402 790Google Scholar
[2] Jedema F J, Filip A T, Wees B J V 2001 Nature 410 345Google Scholar
[3] Heinrich B, Tserkovnyak Y, Woltersdorf G, Brataas A, Urban R, Bauer G E W 2003 Phys. Rev. Lett. 90 187601Google Scholar
[4] Kajiwara Y, Harii K, Takahashi S, Ohe J, Uchida K, Mizuguchi M, Umezawa H, Kawai H, Ando K, Takanashi K, Maekawa S, Saitoh E 2010 Nature 464 262Google Scholar
[5] Heinrich B, Burrowes C, Montoya E, Kardasz B, Girt E, Song Y Y, Sun Y Y, Wu M Z 2011 Phys. Rev. Lett. 107 066604Google Scholar
[6] Rezende S M, Rodriguez S R L, Soares M M, Vilela L L H, Ley D D, Azevedo A 2013 Appl. Phys. Lett. 102 012402Google Scholar
[7] Uchida K, Takahashi S, Harii K, Ieda J, Koshibae W, Ando K, Maekawa S, Saitoh E 2008 Nature 455 778Google Scholar
[8] Uchida K, Xiao J, Adachi H, Ohe J, Takahashi S, Ieda J, Ota T, Kajiwara Y, Umezawa H, Kawai H, Bauer G E W, Maekawa S, Saitoh E 2010 Nat. Mater. 9 894Google Scholar
[9] Weng H M, Yu R, Hu X, Dai X, Fang Z 2015 Adv. Phys. 64 03227Google Scholar
[10] Takahashi S, Maekawa S 2008 Sci. Technol. Adv. Mater. 9 014105Google Scholar
[11] Miao B F, Huang S Y, Qu D, Chien C L 2014 Phys. Rev. Lett. 112 236601Google Scholar
[12] Althammer M, Meyer S, Nakayama H, Schreier M, Altmannshofer S, Weiler M, Huebl H, Geprags S, Opel M, Gross R, Meier D, Klewe C, Kuschel T, Schmalhorst J M, Reiss G, Shen L M, Gupta A, Chen Y T, Bauer G E W, Saitoh E, Goennenwein S T B 2013 Phys. Rev. B 87 224401Google Scholar
[13] Lu Y M, Choi Y, Ortega C M, Cheng X M, Cai J W, Huang S Y, Sun L, Chien C L 2013 Phys. Rev. Lett. 110 147207Google Scholar
[14] Isasa M, Pinto A B, Velez S, Golmar F, Sanchez F, Hueso L E, Fontcuberta J, Casanova F 2014 Appl. Phys. Lett. 105 142402Google Scholar
[15] Shang T, Zhan Q F, Yang H L, Zuo Z H, Xie Y L, Zhang Y, Liu L P, Wang B M, Wu Y H, Zhang S, Li R W 2015 Phys. Rev. B 92 165114Google Scholar
[16] Liao Z L, Li F M, Gao P, Li L, Guo J D, Pan X Q, Jin R, Plummer E W, Zhang J D 2015 Phys. Rev. B 92 125123Google Scholar
[17] Uchida K, Qiu Z Y, Kikkawa T, Lguchi R L, Saitoh E 2015 Appl. Phys. Lett. 106 052405Google Scholar
[18] Putter S, Geprags S, Schlitz R, Althammer M, Erb A, Gross R, Goennenwein S T B 2017 Appl. Phys. Lett. 110 012403Google Scholar
[19] Biswas A, Yang C H, Ramesh R, Jeong M H 2017 Prog. Surf. Sci. 92 02117Google Scholar
[20] Peng R, Xu H C, Xia M, Zhao J F, Xie X, Xu D F, Xie B P, Feng D L 2014 Appl. Phys. Lett. 104 081606Google Scholar
[21] Snyder G J, Hiskes R, DiCarolis S, Beasley M R, Geballe T H 1996 Phys. Rev. B 53 14434Google Scholar
[22] Huang S Y, Fan X, Qu D, Chen Y P, Wang W G, Wu J, Chen T Y, Xiao J Q, Chien C L 2012 Phys. Rev. Lett. 109 107204Google Scholar
[23] Soumyanarayanan A, Raju M, Oyarce A L G, Tan A K C, Im M Y, Petrovi A P, Ho P, Khoo K H, Tran M, Gan C K, Ernult F, Panagopoulos C 2017 Nat. Mater. 16 898Google Scholar
[24] Zhang S, Zhang S S L 2009 Phys. Rev. Lett. 102 086601Google Scholar
[25] Li Y, Kanazawa N, Yu X Z, Tsukazaki A, Kawasaki M, Ichikawa M, Jin X F, Kagawa F, Tokura Y 2013 Phys. Rev. Lett. 110 117202Google Scholar
[26] Belabbes A, Bihlmayer G, Bechstedt F, Blügel S, Manchon A 2016 Phys. Rev. Lett. 117 247202Google Scholar
[27] Meng K K, Zhao X P, Liu P F, Liu Q, Wu Y, Li Z P, Chen J K, Miao J, Xu X G, Zhao J H, Jiang Y 2018 Phys. Rev. B 97 060407Google Scholar
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