2008 年度研究工作进展

(1) 三明治型纳米环状磁性隧道结的制备及其磁矩翻转机制的研究

我们制备出直径为100 nm、环宽为30 nm的三明治型Ta(5 nm)/Cu(20)/Ta(5)/CoFe(5)/ Al-Ox(0.7)/ CoFeB(2.5)/Ta(3)/Ru(5)环状性磁性隧道结及其阵列，并研究了三明治型纳米环MTJ在外磁场和极化电流作用下的磁矩翻转情况。并利用微磁学模拟的方法定量计算了三明治结构纳米环形磁性隧道结中电流产生的奥斯特场和自旋极化电流产生的自旋转力矩效应对磁矩翻转产生的贡献。计算表明极化电流产生的自旋转力矩效应在纳米环形磁性隧道结磁矩的翻转过程中具有决定性的作用；电流产生的奥斯特场对磁矩的翻转起辅助作用。这是其它系统中所没有观察到的现象。微磁学模拟的结果显示：这两种效应的共同作用有助于减小翻转磁矩所需的临界电流，与实验结果相吻合。这一研究成果对于进一步减小临界电流以及降低功耗、提高存储密度具有很好的指导意义[Effects of the current on nano-scale ring-shaped magnetic tunnel junctions, PRB 77 (2008) 134432]。

(2) Co插层对单晶磁性隧道结Fe(001)/MgO(001)/Fe(001)磁电阻的增强效应

对Fe(001)/Co(001)/MgO(001)/Co(001)/Fe(001)单晶磁性隧道结进行了第一性原理计算研究，证实在Fe/MgO界面处插入一至数个原子层的超薄Co(001)膜后能够大幅提高隧穿磁电阻比值[APL 93 (2008) 172501]。该研究结果对发展基于磁性隧道结的自旋电子学器件(如：自旋晶体管、磁随机存储器和磁逻辑等)，具有重要参考价值。相关研究结果被选做该期APL杂志的封面图片。

2008 年会议论文目录

国际会议邀请报告：

[1] Microfabrication of MRAM demo devices based on nano-ring-type magnetic tunnel junctions and spin-polarized current driving,

X. F. Han , The 52nd Annual Conference on Magnetism and Magnetic Materials (MMM 2008) ,

Nov.5-9 , 2008 , Florida, USA.

Invited Paper , X. F. Han, Z. C. Wen and H. X. Wei, J. Appl. Phys. 103 (2008) 07E933.

[2] MRAM demo devices based on spin-polarized current driving and nano-ring-shaped MTJs , XF Han,??? The 3rd Taiwan International Conference

on Spintronics & The 4th Asia Forum on Magnetics , Jul.29-Aug.3 , 2008, YunLin, Taiwan

[3]A novel method to probe spin-flip scattering and spin-flip length in nanoscale layers of magnetic tunnel junctions, XF Han, The International

Conference on Nanoelectronics, Nanostructures, and Carrier Interaction 2008 , Feb.20-23 , 2008 , Kanagawa, Japan

[4] Fabrication of nanoring MTJ and its application in spin-polarized current driving MRAM demo devices, XF Han, The 2008 March Meeting of

the American Physical Society , Mar.3-11 , 2008, Colorado, US

国际会议论文：

[1]Nanoring magnetic tunnel junction and its application in magnetic random access memory demo devices with spin-polarized current switching, XF Han, The 52nd Annual Conference on Magnetism and Magnetic Materials (MMM 2007), Nov.05 -09 2007, Tampa, Florida, USA

[2]Tunneling magnetoresistance in CoFeB/GaAs/ (Ga,Mn)As hybrid magnetic tunnel junctions, GX Du, The 52nd Annual Conference on Magnetism and Magnetic? Materials (MMM 2007), Nov.05 -09, 2007, Tampa, Florida, USA)

[3]Linear magnetic field response spin valve with perpendicular anisotropy ferromagnet layer, QH. Qin , The 52nd Annual Conference on Magnetism and Magnetic Materials (MMM 2007), Nov.05 -09, 2007, Tampa, Florida, USA）

国内会议邀请报告：

[1]Patterned nano-ring magnetic tunnel junctions and nano-ring MRAM demo devices , XF Han , The 1st Chinese-French Workshop on Quantum Manipulation of Spins in Semiconductors , Oct.15-19 , 2008 , Beijing, China

[2]Design and fabrication of nano-ring MRAM demo devices based on spin-polarized current driving, XF Han, China National Conference on Functional Materials and Applications, Nov.15-19, 2008, Wuhan, China

[3]Nanoring magnetic tunnel junctions and nanoring MRAM demo devices, XF Han , The 11th Chinese Conference of Low Temperature Physics , Aug.10-14 , 2008 , Haerbin , China

2008 年发表学术论文目录

[1] Nano-scale Patterned Magnetic Tunnel Junction and Its Device Applications, X. F. Han, Z. C. Wen, Y. Wang, L. Wang and H. X. Wei, AAPPS Bulletin 18 (6) (2008) 24-32.

[2] Magnetic proximity effect at the molecular scale: First-principles calculations, D. P. Liu, Y. B. Hu, H. Guo, and X. F. Han, Physical Review B, 78, (2008), 193307.

[3] Temperature dependence of giant tunnel magnetoresistance in epitaxial Fe/MgO/Fe MTJs, S. G. Wang, R. C. C. Ward , G. X. Du , X. F. Han, C. Wang, and A. Kohn, Physical Review B, 78, (2008), 180411(R).

[4] Current-induced multiple spin structures in 100-nm nanoring magnetic tunnel junctions, H. X. Wei , F. Q. Zhu, X. F. Han, Z. C. Wen, C. L. Chien, Physical Review B, 77, (2008), 224432 .

[5] Theory of nonspecular tunneling through magnetic tunnel junctions, X.-G. Zhang, Y. Wang, and X. F. Han, Physical Review B, 77, (2008), 144431

[6] Effects of the current on the nanoscale ring-shaped magnetic tunnel junctions, H. X. Wei , J. X. He, Z. C. Wen, X. F. Han, S. Zhang, Physical Review B, 77, (2008), 134432.

[7] Current-induced magnetization switching in a microscale ring-shaped MTJ, H. X. Wei, M. C. Hickey, G. I. R. Anderson, X. F. Han, and Christopher H. Marrows, Physical Review B, 77, (2008), 132401.

[8] Effect of Co interlayers in Fe/MgO/Fe magnetic tunnel junctions, Y. Wang, X. F. Han and X. G. Zhang, Applied Physics Letter, 93, (2008), 172501

[9] Space-charge trap mediated conductance blockade in MTJs with half-metallic electrodes, J.F. Feng, T.H. Kim, X.F. Han, X.G. Zhang, Y. Wang, J. Zou, D.B. Yu, H. Yan, A.P. Li, Applied Physics Letter, 93, (2008) 192507.

[10] Magnetic switching of ferromagnetic nanotubes, R.Sharif, S. Shamaila, M.Ma , L.D. Yao, R.C. Yu, X. F. Han, M. Khaleeq-ur-Rahman, Applied Physics Letter, 92, (2008), 032505.

[11] Nanoring MTJ and its application in MRAM demo devices with spin-polarized current switching（invited), X.F. Han, Z.C. Wen, and H.X. Wei, Journal of Applied Physics, 103, (2008), 07E933.

[12] Tunneling magnetoresistance in CoFeB/GaAs/(Ga, Mn)As hybrid magnetic tunnel junctions, G. X. Du, X.F. Han, J. J. Deng, W. Z. Wang, and J. H. Zhao, Journal of Applied Physics, 103, (2008), 07D10.

[13] Linear magnetic field response spin valve with perpendicular anisotropy ferromagnet layer, Q.H. Qin, H.X. Wei and X. F. Han, Journal of Applied Physics, 103, (2008), 07E906.

[14] Effect of Ir–Mn composition on exchange bias and thermal stability of spin valves with nano-oxide layers, Y.F.Liu, J. W. Cai, W. Y. Lai, and G. H. Yu, Journal of Applied Physics, 103, (2008), 093908.

[15] Perpendicular anisotropy dependence of oscillatory interlayer coupling behavior in [Pt/Co]5/Ru/ [Co/Pt]5 multilayers, J. Zhao, Y. J. Wang, Y. Z. Liu, X. F. Han, and Z. Zhang, Journal of Applied Physics, 104, (2008), 023911.

[16] Magnetic and magnetization properties of electrodeposited fcc CoPt nanowire arrays, S. Shamaila, R. Sharif, S. Riaz, M. Ma, M. Khaleeq-ur-Rahman, and X. F. Han, Journal.of Magnetism and Magnetic Materials, 320, (2008), 1803

[17] Magnetic and microstructural characterizations of CoFe and CoFeB nanowires, R. Sharif , S. Shamaila,M. Ma, L. D. Yao, R. C. Yu, X. F. Han, M. Khaleeq-ur-Rahman, Journal Magnetism and Magnetic Materials, 320, (2008), 1512.

[18] Fabrication and magnetic characterization of CoxPt1-x nanowire arrays, S. Shamaila, R. Sharif, S. Riaz, M. Khaleeq-ur-Rahman, X.F. Han, Applied Physics A, 92, (2008), 687.

[19] Structural characterization and temperature dependence of tunnel magnetoresistance in epitaxial Fe/MgO/Fe junctions, S. G. Wang, R. C. C.Ward, G. X. Du, X. F. Han, C. Wang, and A. Kohn, IEEE Transactions on Magnetics, 44 (11), (2008), 2562.

[20] Surface plasmonpolaritonsassisteddiffractioninmetal films with subwavelengthholearray, X. Fang, H. X. Wei, M. Kamran, J. Y. M a, H. Y. Zhao, X. F. Han, X. G. Qiu, Journal of Physics and Chemistry of Solids. 69, (2008), 3093.

[21] Lattice mismatch induced weak perpendicular anisotropy in Fe/Co multilayers prepared by direct current magnetron sputtering, A.L. Xia, H.L. Zhang, L.N. Tong, and B.S. Han, Thin Solid Films, 516, (2008) 7653.

[22] Magnetic microstructures of phase-separated Sm-Co 2:17 type sintered magnets, Y. K. Fang, H.W. Chang, Z.H. Guo, T. Liu, X.M. Li, W. Li, W.C. Chang, B.S. Han, Journal of Alloys and Compounds, 462, (2008), 376.

[23] Comparison of magnetic properties of Fe/Co multilayers prepared by DC magnetron sputtering on glass and Si substrates, A. L. Xia and B. S. Han, Acta Physica Sinica, 57, (2008), 545.

[24] Preparation and characterization of room-temperature ferromagnetic Ni-doped TiO 2 nanobelts, H. Zhang, T. Ji, L. Li, X. Qi, Y. Liu, J. Cai, H. Du, J. Sun , Acta Physico-Chimica Sinica, 24(4), (2008), 607.

[25] Magnetic domain structures of precipitation-hardened SmCo 2:17-type sintered magnets: Heat treatment effect, X. M. Li, Y. K. Fan, Z. H. Guo, T. Liu, Y. Q. Guo, W. Li, and B. S. Han, Chinese Physics B,17, (2008),2281.

国际合作与人员互访交流情况

2008 年由 M02 组负责主要接待工作的来访讲学和合作交流人员：

2008 年 M02 组派出合作交流人员 :

人才培养

2008 年研究生毕业论文