1. 2003/12/1-4International Workshop on "Physics on Nanoscale Magnets", Kyoto Ferromagnetic-Metal Nanoparticle Systems: A Possible Candidate for Left-Handed Materials Satoshi Tomita PRESTO, Japan Science and Technology Agency (JST) s-tomita@riken.go.jp

2. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto acknowledgment Dr. Masayuki Hagiwara (RIKEN) Dr. Kouichi Katsumata (RIKEN) Dr. Kazuo Takeuchi (RIKEN) Dr. Kensuke Akamatsu (Konan Univ.) Dr. Minoru Fujii (Kobe Univ.) Prof. Shinji Hayashi (Kobe Univ.) Prof. Sukekatsu Ushioda (Tohoku Univ. & JST)

3. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto outline 1.Ferromagnetic-metal nanoparticle systems and left-handed materials 2.Preparation of nanoparticle systems 3.Ferromagnetic resonance study 4.Summary & Future works

4. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto outline 1.Ferromagnetic-metal nanoparticle systems and left-handed materials 2.Preparation of nanoparticle systems 3.Ferromagnetic resonance study 4.Summary & Future works

5. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto ferromagnetic-metal nanoparticle systems particle size d particle volume fraction v lowhigh small large nanometer-size particles with low volume fraction Gained widespread Interest in fundamental physics and technology Electromagnetism of matter: A possible candidate for left-handed materials

6. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto left-handed materials Material with both permittivity (  and permeability (  negative Left-Handed Materials :LHMs (Double Negative Materials :DNM) Extraordinary electromagnetic response (Veselago, Usp. Fiz. Nauk 1964.) e.g., inverse Doppler shift, negative index of refraction EE HH k k S=ExH LHMs RHMs

7. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto perfect lens Slab of LHMs can focus EM wave using anomalous refraction Focusing evanescent wave Breaking the diffraction limit “Perfect lens” Pendry, PRL 2000.

8. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto left-handed materials Material with both permittivity (  and permeability (  negative Left-Handed Materials :LHMs (Double Negative Materials :DNM) Extraordinary electromagnetic response (Veselago, Usp. Fiz. Nauk 1964.) e.g., inverse Doppler shift, negative index of refraction EE HH k k S=ExH LHMs RHMs Not yet been found in nature.

9. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto problem LHMs have not yet been found in nature. - Why ??? -Because there is no “negative  ” in nature. cf. negative  in electric plasma cf. absence of magnetic monopole Problem: How can we obtain “negative  ” artificially ?

10. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto routes to LHMs Q. How can we obtain “negative  ”  A1. Resonance in split-ring resonators Pendry et al., IEEE Trans. MW. 1999. A2. Ferromagnetic resonance (FMR) in ferromagnetic-metal (FM-M) nanoparticle systems Chui and Hu, PRB 2002.

11. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto split-ring resonators (SRR) -negative  -  as a function of f [GHz]: simulation Smith et al., PRB 2001. a 2r d volume fraction of rings: F=  r 2 /a 2 capacitance between rings: C=  0 /d Pendry et al., IEEE Trans. MW. 1999. Quasi magnetic plasma with positive effective mass negative  eff i out i in +++ - - -

12. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto meta-materials Meta-materials by UCSD group Shelby, Smith, and Schultz, Science 2001. Assembles arrays of split-ring resonators and metallic wires into meta-materials Shelby et al., APL 2001.

13. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto left-handed meta-materials Microwave transmission experiment Shelby et al., APL 2001  and  of meta-materials Smith et al., PRB 2001. Calculation:Experiments: Negative refraction of microwave by LH meta-materials Shelby et al., Science 2001.

14. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto routes to LHMs Q. How can we obtain “negative  ”  A1. Resonance in split-ring resonators Pendry et al., IEEE Trans. MW. 1999. A2. Ferromagnetic resonance (FMR) in ferromagnetic-metal (FM-M) nanoparticle systems Chui and Hu, PRB 2002. Ferromagnetic-metal nanoparticle Insulating matrices

15. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto theoretical consideration Effective medium approximation Low volume fraction of particles Controlling the direction of magnetization FMR with positive circularly polarized microwave A film of Left-Handed Materials Ferromagnetic-metal nanoparticle Insulating matrices Chui and Hu, Phys. Rev. B 2002

16. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto ferromagnetic resonance  0 /   ： Ferromagnetic Resonance (FMR) 00 0 1  ++ Negative   H+H+ x y Positive circularly polarized microwave (w 0 )  Magnetic moment under H ext = H 0 ： Larmor frequency  L  0  M x y z H ext =H 0  Under the constant H ext =H 0

17. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto FM-M nanocomposite for LHMs 00   0 0 1    < 0 @ below plasma frequency of metal (  p )   < 0 @ vicinity of FMR frequency (  0 ) FM-M nanocomposite films LHMs at vicinity of a FMR frequency (microwave region) low eddy current loss

18. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto eddy current losses M 2r 0 To suppress eddy current losses: Small r 0 Small P (eddy current loss) Uniform magnetization along a magnetic cylinder with diameter of 2r 0 Eddy current loss (P): Chikazumi, Physics of Ferromagnetism

19. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto this project Present study: 1.Preparation of FM-M nanocomposite films 1.1 Fe-SiO 2 nanocomposite films by co-sputtering 1.2 Ni-Polyimide nanocomposite films by Chemical Implantation Technique 2. FMR studies of nanocomposite films FMR condition of the nanocomposite films Mission: Realization of LHMs using FM-M nanocomposite by Innovative Nanotechnology Integration, PRESTO, JST http://www.nano-integ.jst.go.jp

20. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto outline 1.Ferromagnetic-metal nanoparticle systems and left-handed materials 2.Preparation of nanoparticle systems 3.Ferromagnetic resonance study 4.Summary & Future works

21. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto chemical implantation Scheme of Ni nanoparticle implantation into polyimide (PI) films PMDA-ODA type polyimide film （ Kapton 200-H ） Step1: KOH treatment Step2: NiCl 2 treatment Step3: Thermal annealing in H 2 atomospher ion exchange Ni-PI nanocomposite films imide ring carboxylic acid reduction re-imidizaation particle growth

22. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto Ni-PI nanocomposite films PINi nanoparticles Composite layer Initial thickness ： 4  m Ni-PI: 300 ºC-30min Cross-sectional TEM image fcc-Ni nanoparticles d ave = 9.1 nm  = 1.0 nm Annealing temperature ⇒ diameter of Ni nanoparticles （ d ave ）

23. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto composite thickness Cross-sectional TEM images of films annealed at 300 ºC 30 min. 2.7  m 120 min. 0.53  m

24. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto volume fraction of Ni Average volume fraction of Ni in composite layers: v ave [%] N: amount of Ni ions estimated by ICP t : thickness of composite layers estimated by TEM Long-time annealing shrinks the composite layer Decrease in thickness of composite layers → Increases in effective volume fraction of particles t eff : effective thickness of Ni in the composite layers

25. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto control over volume fraction 300 ºC 5 min.: v = 2 % 30 min.: v = 4 % 120 min.: v = 21 % Control over volume fraction of Ni nanoparticles with constant diameter control over interparticle distance Thickness, volume fraction and diameter plotted as a function of annealing time

26. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto outline 1.Ferromagnetic-metal nanoparticle systems and left-handed materials 2.Preparation of nanoparticle systems 3.Ferromagnetic resonance study 4.Summary & Future works

27. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto ferromagnetic resonance H  FMR uniform mode (Kittel mode)  =0 ° : red line 3000 Oe (lower field)  =90° : blue line 3200 Oe (higher field) Can be explained by “Kittel equation” FMR signal by an X-band (f=9.1GHz) conventional EPR spectrometer. Angular dependence at R.T. v=2.1%

28. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto Kittel equation Rotational ellipsoidal magnet Magnet disk (  =0°): N x =N z =0, N y =4  Magnet disk (  =90°) : N x =N y =0, N z =4  H0H0 H0H0 H0H0 N x, N y, N z : demagnetization factor N x +N y +N z = 4  x x y y z z x z y C.Kittel, Introduction to Solid State Physics.

29. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto magnetic coupling Ni particles are separated but coupled by magnetic interaction X-band (f=9.1GHz) FMR signals. Angular dependence at R.T. Film behaves macroscopically as a thin magnetic films

30. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto tuning resonance field Resonance field vs volume fraction Resonance field can be tuned by volume fraction X-band (f=9.1GHz) FMR signal. R.T. Angular dependence

31. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto multi-frequency FMR cf: Bulk Ni: g=2.21 Ni-PI× ３４ Without cavity H=0-14T swept Simple transmission of MW f=30-413GHz fixed... Applied magnetic field for resonance increases with microwave frequency, and vice versa Multi-freq. FMR resonance condition

32. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto resonance tunability Volume fraction determines the demagetization term: 4  M z In perpendicular configuration: Resonance frequency  0 can be tuned by applied magnetic field H 0, in principle. Advantage: Frequency tunability and high-frequency operation Under a given H 0 : H 0 – 4  M z =  0 /|  | sweep  00  0 1   0 1  H ext =H 0 0’0’ H ext =H 0 ’>H 0

33. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto summary We have studied ferromagnetic resonance in ferromagnetic-metal nanocomposite films as a possible candidate for left-handed materials.  Ni nanoparticles are chemically implanted in polyimide films.  Ferromagnetic resonance can be observed up to 400 GHz.  FMR condition can be tuned by volume fraction and applied magnetic field, suggesting a possibility for tuning a frequency where the material becomes left-handed.

34. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto future works 1.Characterization of  2.Material design for negative  3.Microwave transmission experiment with frequency sweep Thanks a lot for your attention. Email: s-tomita@riken.go.jp URL: http://www.nano-integ.jst.go.jp

35. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto microwave Microwave: Frequency 3GHz ～ 300GHz (Wavelength 10cm ～ 1mm) (Wavelength)Frequency LF (1km)300kHz MF (100m)3MHz HF (10m)30GHz VHF (1m)300MHz UHF (10cm)3GHz SHF (1cm)30GHz EHF (1mm)300GHz (Terahertz) (Far-infrared) (700 ～ 400nm) (Visible) H+H+ x y Positive circularly polarized microwave:  0 in the range of GHz 

36. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto Larmor precession M x y z  M x y z Magnetic moment under external magnetic field H ext ： Precession with Larmor frequency (  L ) in the range of GHz H ext LL

37. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto preparation technique Controlling the microstructure of FM-M nanocomposite films Particle size: several nanometer Distribution: dispersed uniform Volume fraction: controllable independently (20-30 % by Chui et al. PRB 2002) Difficult in the conventional methods e.g., sputtering, deposition, decomposition We have developed a novel technique: Chemical Implantation Technique

38. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto resonance tunability Volume fraction (magnetic interaction) determines the strength of demagetization effect: 4  M z In perpendicular configuration: Under constant  o :  0 /|  | + 4  M z = H 0 sweep H 0 Under constant Ho: H 0 – 4  M z =  0 /|  | sweep  0

39. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto high-frequency FMR Ni-PI FMR f=333GHz 100K Ni-PI× ３４ (total composite thickness 88  m) Without cavity H MW f=333GHz... Resonance observed Not using cavity

40. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto electromagnetic response ε  Transparent media  > 0 and  >0 n=(  ) 1/2 :real Air Left-Handed Materials  < 0 and  <0 Electromagnetic response of matter Electrical permittivity (  ) and magnetic permeability (  ) ⇒ Index of refraction (n): n = (  ) 1/2 Air  0 n: imaginary Plasma Air  > 0 and  <0 n: imaginary SRR ???

41. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto split-ring resonator Q. How can we obtain “negative  ”  A1. Split-ring resonators Pendry et al., IEEE Trans. MW. 1999.  as a function of f [GHz]: simulation Smith et al., PRB 2001.

42. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto metal wires - negative  -  as a function of f [GHz]: simulation Smith et al., PRB 2001. Very low electron density (n eff ) and Very large electron effective mass (m eff ) Electric plasma at extremely low frequency: Extremely low  ep Negative  eff in microwave Pendry, et la., PRL 1996. 2r a

43. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto negative index of refraction Experimental setup for verification of negative refraction Shelby et al., Science 2001. Negative refraction of microwave by LH meta-materials Shelby et al., Science 2001.

44. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto meta-material? or material? LHMs obtained are Not material But meta-material From the view point of application, Material-like LHMs is required. Another candidate: Ferromagnetic-metal nanocomposite films

45. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto Fe-SiO 2 nanocomposite v=15% cross-sectional TEM and size distribution v=5% : d=~1nm v=15%: d=2.01 nm (  =0.17nm)

46. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto FMR angular dependence FMR spectra (a) v=5% 、 (b) v=15%  H v=5%: v=15%:  =0°  =90°

47. 2003/12/1-4 International Workshop on "Physics on Nanoscale Magnets", Kyoto magnetization ZFC-FC magnetization w/|  |=H 0 -4  M z