JST-DFG workshop on Nanoelectronics January 22, 2009, Karasuma Kyoto Hotel Nanostructure and properties of magnetic materials K. Hono and T. Ohkubo National Institute for Materials Science and d International Center for Materials Nanoarchitronics Development of Nanostructured Materials -understanding propety-structure relationships -understanding the roles of alloying elements Process •sputtering •rapid solidification rapid solidification •mechanical milling •sintering •themomechanical process tuning •phase transformation cluster precipitate nanocrystal nanocomposite Properties ・ magnetic ・ spintronics structure & properties amorphous amo/nano nanogranular multilayer ・ mechanical mechanical multiscale characterization Nanostructured Metallic Materials •permanent magnets •nanocrystalline soft magnetic materials 3DAP •Magnetic recording media SEM/FIB TEM •spintronics materials •spintronics devices -TMR, CPP-GMR •nanostructured high strength alloys 1
Chemical analysis by TEM EDS Acquire EDX Nd Nd 1000 Dy Nd Counts Nd Nd Fe 500 O Dy Fe Nd Dy Fe Dy Dy Fe Nd Dy Nd Nd Dy Nd Nd Dy Dy Fe Dy Dy Dy 0 0 2 4 6 8 10 Energy (keV) STEM/HAADF Co O Fe Ni HREM EELS SAED TEM image – 2D projection Energy filtering TEM tomography 3D atom probe Field ion microscope 3-D atom probe Sm 2 Co 17 V p Nd 4.5 Fe 77 B 18 Cu 0.2 m / n =2 eV e ( t / l ) 2 V dc 2
(Fe 0.85 B 0.15 ) 100-x Cu x nanocrystalline softmagnets x =1.0 ・ Fe ・ B ・ Cu 40 nm 2 nm x =1.5 18 nm 80 nm 3 nm 1 h @390 C Site specific specimen preparation for 3DAP W needle microsampling In FIB Ga + annular beam AP specimen ~1 m ~200 nm ~100 nm bond b d Cu tube 3
Laser assisted wide angle 3DAP Position sensitive detector FIM tip E dc + E p r = ~ 50 nm V dc ~5 kV Position ( x i , y i ) ( i , y i ) Pulsed Laser Timer HV 3D Data Software Dilute ferromagnetic semiconductor thin films Mn (Ga 0.95 Mn 0.05 ) 0.5 As 0.5 100 nm Substrate: Zn doped p + S Ga 0.5 As 0.5 (001) Ga As ~ 20 nm ~ 40 nm D. Chiba, F. Matsukura, and H. Ohno, APL 89 , 162505 2006. M. Kodzuka et al. Ultramicroscopy (2009) in press. 4
Nanostructure analysis of GaInN laser diodes for blue-ray devices ・ 6 MQW (In~0.25, 0.15, 0.08) InGaN Well ~3nm GaN Barrier ~14nm Pt デポ ～ 100nm Ni ～ 500nm Ni 5nm Au 5nm GaN ~5nm In0.25GaN I 0 25G N GaN In0.15GaN GaN 65nm In0.08GaN GaN In0.25GaN 55nm GaN In0.15GaN GaN In0.08GaN GaN ~0.5um Sapphire sub After Tomiya @ SONY 200nm Demand of permanent magnets for HV&EV Hybrid viehcle, electric viehcle 400 371 43 ％ 43 ％ 300 300 260 260 increase 予測 Dy 量 - ｔ／年 227 227 200 Operation temperature: 200 C 13 227 13 others 100 150 PC 131 12 HEV 21 0 H16 17 18 19 20 21 22 27 年 5
Nd-Fe-B sintered magnets Nd 2 Fe 14 B Nd-rich Nd,Dy Fe B Nd 2 Fe 14 B K 1 (Dy) >> K 1 (Nd) Fe Nd Dy Magnetization reversal by the nucleation mechanism H Nd-rich Nd-rich Nd 2 Fe 14 B Nd 2 Fe 14 B M r M Nd 2 Fe 14 B M s Nucleation type SD H c ~0.15H A H H A H A H H c Demagnetized state 6
FIM specimen preparation using FIB Microstructure before Annular milling FIB annular milling annular milling from the top to from the top to fabrication fabrication sharp tip Grain Grain boundary boundary Nd FIB rich cutting NdFeB tip Question #1 Why Hc increase by trace Cu addition? Nd Dy Cu B Fe H c (kOe) Sample (at.%) (at.%) (at.%) (at.%) (at.%) NdFeB 14.6 0 0 6.1 79.4 3.6 NdFe(Cu)B 14.6 0 0.13 6.1 79.2 13.6 NdFe(Cu)B Annealing condition under magnetic field 140kOe, 550 C × 3 h quench without magnetic field f NdFeB 7
Serial sectioning BSE images NdFeB NdFe(Cu)B 5 m 3D tomography of Nd-rich phase NdFeB NdFe(Cu)B 8
HR BSE images of GBs of Nd-Fe-B magnets NdFeB NdFe(Cu)B HREM of grain boundaries of Nd-Fe-B magnets NdFeB NdFe(Cu)B Interface in not clear Observation direction Decrease the magnetic anisotropy → H c is decreased c 9
NdFe(Cu)B ~2nm 3DAP analysis of grain boundary Nd 41 Fe 33 Cu 25 B Nd 12 Fe 82 B 5 Cu 10
Nd 3DAP analysis NdFe(Cu)B Fe 1.0 1 0 Composition Profile B Fe B 0.8 Nd Cu O Composition 0.6 stoichiometry ： Nd 12 Fe 82 B 6 Cu 0.4 0.2 O 0.0 0 5 10 15 20 25 Distance/nm Nd 35 Fe 28 Cu 11 O 26 Nd 13 Fe 79 Cu 2 B 5 O 1 ～ 30nm As sintered Annealed Nd 2 Fe 14 B 2 14 Nd 2 Fe 14 B Nd 2 Fe 14 B Nd, Cu rich Nd rich 11
Nd-Fe-B sintered magnets Nd 2 Fe 14 B Nd-rich D GB ~1.5 D powder W. F. Li et al. JMMM, (2009) in press. H ydrogenation D isproportionation D esorption R ecombination ( HDDR ) Process t DR 2NdH 2 + 12Fe + Fe 2 B F B 2NdH 12F Nd 2 Fe 14 B + 2H 2 Nd 2 Fe 14 B + 2H 2 2NdH 2 + 12Fe + Fe 2 B Nd 12.5 Fe 73 Co 8 B 6.5 After T. Nishiuchi and S. Hirosawa, Hitachi Metals 12
0 min 8 min NdH 2 Nd 2 Fe 14 B α -Fe NdH 2 -Fe 20min Fe 3 B 15min 15 min 20 min Nd 2 Fe 14 B 8min 0min Nd 2 Fe 14 B Nd-rich NdH 2 500nm TEM bright field images Nd map Nd map DR 15 min DR 20 min 13
Grain boundaries of HDDR powder DR 15 min DR 20 min Specimen preparetion from powder HDDR FIB fabrication Put sample on powder the W needle Deposition Cut and lift out Cutting W needle Annuar milling Deposition 14
3DAP analysis of HDDR powder ~30nm 30 Nd 19.8 Fe 63.2 Co 13.7 B 3.4 Nd 13.6 Fe 68.9 Co 12.9 B 4.6 Nd 13.3 Fe 70.4 Co 12.4 B 4.0 Sintered and HDDR magnets Sintered HDDR 15
H c increase by optimizing interfacial nanostructure SD How? Summary •There is a large potential in developing higher performance performance magnetic magnetic materials materials by by controling controling nanostructures •Nanostructure characterization by 3DAP/TEM is particularly useful to obtain critical information on designing nanostructured magnetic materilals •Laser assisted wide angle 3D atom probe expands the application area of 3DAP including semiconductors and their thin film devices 16
Acknowledgment NIMS: W.F. Li Univ. Tsukuba: M. Kodzuka, Y. M. Chen Hitachi Metals: S. Hirosawa, T. Nishiuchi Funding Agencies CREST-JST for laser assisted 3D atom probe TOYOTA and NEDO for permanent magnet research 17
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