Nanostructure and properties of magnetic materials K. Hono and T. - - PDF document

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Nanostructure and properties of

JST-DFG workshop on Nanoelectronics January 22, 2009, Karasuma Kyoto Hotel

• K. Hono and T. Ohkubo

National Institute for Materials Science d

magnetic materials

and 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
• phase transformation

Properties

・magnetic

・spintronics ・mechanical

cluster precipitate nanocrystal nanocomposite amorphous amo/nano nanogranular multilayer

structure & properties process tuning

mechanical Nanostructured Metallic Materials

3DAP TEM SEM/FIB

• permanent magnets
• nanocrystalline soft magnetic materials
• Magnetic recording media
• spintronics materials
• spintronics devices -TMR, CPP-GMR
• nanostructured high strength alloys

multiscale characterization

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Chemical analysis by TEM

EDS

STEM/HAADF Co O

TEM image – 2D projection

HREM SAED Energy filtering TEM tomography Fe Ni EELS

3D atom probe

Field ion microscope 3-D atom probe

Sm2Co17

Vdc Vp

Nd4.5Fe77B18Cu0.2

m/n=2eVe(t/l)2

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・ Fe ・ B ・ Cu

(Fe0.85B0.15)100-xCux nanocrystalline softmagnets

x=1.0

40 nm 2 nm

x=1.5

1 h @390C 80 nm 18 nm 3 nm

W needle

microsampling In FIB

Site specific specimen preparation for 3DAP

b d

~200 nm ~1 m

AP specimen

Ga+ annular beam

~100 nm

bond

Cu tube

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Edc

Position sensitive detector

FIM tip

Vdc ~5 kV

+Ep Position (xi,yi)

Laser assisted wide angle 3DAP

r = ~ 50 nm

HV

3D Data Software

( i,yi)

Timer

Pulsed Laser Mn

Dilute ferromagnetic semiconductor thin films

(Ga0.95Mn0.05)0.5As0.5 S

100 nm Ga

Substrate: Zn doped p+ Ga0.5As0.5 (001)

~ 40 nm ~ 20 nm

As

• D. Chiba, F. Matsukura, and H. Ohno,

APL 89, 162505 2006.

• M. Kodzuka et al. Ultramicroscopy (2009) in press.

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GaN ~5nm I 0 25G N

Ni ～500nm Ni 5nm Au 5nm Ptデポ ～100nm ・6 MQW (In~0.25, 0.15, 0.08) InGaN Well ~3nm GaN Barrier ~14nm

Nanostructure analysis of GaInN laser diodes for blue-ray devices

65nm 55nm

In0.25GaN GaN In0.15GaN GaN In0.08GaN GaN In0.25GaN GaN In0.15GaN GaN In0.08GaN

200nm

Sapphire sub GaN ~0.5um

After Tomiya @ SONY

Demand of permanent magnets for HV&EV

Hybrid viehcle, electric viehcle

400 300 371

43％

Operation temperature: 200C

260 300 200 100 予測Dy量-ｔ／年

43％ increase

13 227 227 13

• thers

260 227

H16 17 18 19 20 21 22 27

年 131 150

HEV PC

12 21

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Nd-Fe-B sintered magnets

Nd2Fe14B

Fe B Nd,Dy

Nd-rich

Nd Fe Dy

K1(Dy) >> K1(Nd)

Nd2Fe14B

Magnetization reversal by the nucleation mechanism

H

Nd-rich Nd2Fe14B Nd-rich

Nucleation type H M H Mr Ms

Nd2Fe14B

Nd2Fe14B

Hc~0.15HA

HA SD Hc Demagnetized state HA

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FIB fabrication Microstructure before annular milling Annular milling from the top to

FIM specimen preparation using FIB

Nd rich Grain boundary Grain boundary FIB cutting fabrication annular milling from the top to sharp tip NdFeB tip

Question #1 Why Hc increase by trace Cu addition?

Sample Nd (at.%) Dy (at.%) Cu (at.%) B (at.%) Fe (at.%) Hc (kOe) NdFeB 14.6 6.1 79.4 3.6

Annealing condition under magnetic field 140kOe, 550C×3 h f

NdFe(Cu)B 14.6 0.13 6.1 79.2 13.6

NdFe(Cu)B quench without magnetic field NdFeB

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5m

NdFeB NdFe(Cu)B

Serial sectioning BSE images

3D tomography of Nd-rich phase

NdFeB NdFe(Cu)B

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NdFeB NdFe(Cu)B

HR BSE images of GBs of Nd-Fe-B magnets

HREM of grain boundaries of Nd-Fe-B magnets

NdFeB NdFe(Cu)B Interface in not clear Decrease the magnetic anisotropy → Hc is decreased

Observation direction

c 

10 NdFe(Cu)B

~2nm

3DAP analysis of grain boundary

Nd41Fe33Cu25B Nd12Fe82B5Cu

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1 0

3DAP analysis NdFe(Cu)B

Nd Fe

0.4 0.6 0.8 1.0

Composition B Fe Nd Cu O

Composition Profile

B Cu

stoichiometry： Nd12Fe82B6

5 10 15 20 25 0.0 0.2

Distance/nm ～30nm

O Nd35Fe28Cu11O26 Nd13Fe79Cu2B5O1

As sintered Annealed

Nd2Fe14B Nd2Fe14B

2 14

Nd2Fe14B Nd, Cu rich Nd rich

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Nd-Fe-B sintered magnets

Nd2Fe14B Nd-rich

DGB~1.5Dpowder

• W. F. Li et al. JMMM, (2009) in press.

Hydrogenation Disproportionation Desorption Recombination (HDDR) Process

tDR

2NdH 12F F B  2NdH2 + 12Fe + Fe2B  Nd2Fe14B + 2H2 Nd2Fe14B + 2H2  2NdH2 + 12Fe + Fe2B

Nd12.5Fe73Co8B6.5

After T. Nishiuchi and S. Hirosawa, Hitachi Metals

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0 min 8 min

NdH2 Nd2Fe14B α-Fe NdH2 20min -Fe Fe3B

15 min 20 min

Nd2Fe14B Nd-rich Nd2Fe14B 0min 8min 15min

500nm

NdH2

TEM bright field images

Nd map Nd map DR 15 min DR 20 min

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Grain boundaries of HDDR powder

DR 15 min DR 20 min

HDDR powder FIB fabrication Put sample on the W needle

Specimen preparetion from powder

Cut and lift out W needle Deposition Cutting Deposition Annuar milling

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3DAP analysis of HDDR powder

30 ~30nm

Nd13.3Fe70.4Co12.4B4.0 Nd19.8Fe63.2Co13.7B3.4 Nd13.6Fe68.9Co12.9B4.6

Sintered and HDDR magnets

Sintered HDDR

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Hc increase by optimizing interfacial nanostructure

SD

How?

Summary

• There is a large potential in developing higher

performance magnetic materials by controling performance magnetic materials by 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

• f

3DAP including semiconductors and their thin film devices

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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