Magnetic Nanoparticles: Challenges and Future Prospects

June 18-22, 2007, Leiden

Sam Bader

Materials Science Division and

Center for Nanoscale Materials

Argonne National Laboratory

Opportunitiesin

Nanomagnetism*

* Work supported by U.S. DOE Office of Science,Basic Energy Science – Materials Science

under Contract No. DE-AC02-06CH11357.

2

400 years later…"De Magnete”, William Gilbert

1600

William Gilbert

3

The Quest…

4

Grand Challengesin

Nanomagnetism

Ultra StrongPermanentMagnets

~100% Spin Polarized

Materials

Ultra HighDensityMedia

Spin TransistorWith Gain

R.T. Magnetic Semiconductors

Magnetic Logic

Spin-BasedQubits

Instant Boot-UpComputer

HierarchicallyAssembled

Media

Computer From

Test Tube

Nano-BioMag Sensors

Ultimate Limits of

MiniaturizationEase of

Manufacture

SpinTransport

SpinDynamics

5

Principles of Nanoscience

6

)(EN↑)(EN↓

F1 F2

N

Concept of Lateral Spin ValveV

MIMδ

)(EN↑)(EN↓

E E

e-

)(EN↑)(EN↓

E

parallel

)(EN↑)(EN↓

Eanti-parallel

sV

L

F1 N F2 F2

7

a.c. current source

Lock-in detection

H

1 µm

Py = NiFe

I

V

Injector

Detector

Spin Injection, Diffusion, and Detection inLateral Spin-Valves

λs = 63 ± 15 nmYi Ji et al. APL 85, 6218 (2004)

T = 10 K

H (Oe)--200200 --100100 00 100100 200200 300300 400400--

Spin-Orbit Effects

1 µm

8

Magnetization reversal due to formation of the magnetic vortex state in circular dot

-150 -100 -50 0 50 100 150

-1.0

-0.5

0

0.5

1.0 (e)

(c)

(d)

(b) (a) M

agne

tizat

ion,

M/M

s

Field, mT

(a) (b) (c) (d) (e)

HH

Magnetic Vortex State in Disk-shaped Nanomagnets

9

Vortex Dynamics in the Frequency Domain

V. Novosad, F. Fradin, P. E. Roy, K. Buchanan, K. Guslienko, and S. D. Bader, Phys Rev. B, B 72, 024455 (2005).

50 100 150 200 250 300 350

0.0

0.5

1.080 MHz 160 MHz 272 MHz

L=20nm, 2R=2um L=40nm, 2R=2um L=40nm, 2R=1um

Disp

ersio

n D

eriv

ativ

e (A

rb. U

nits)

Frequency (MHz)

Magnetic disks on a waveguide

3 µm

Vortex core trajectory

Shifted vortexcore position

•Measure impedence change due to magnetic resonance•Sweep frequency and magnetic field

10

Magnetic Vortex Configurations

c = chirality

p = polarity V. Rose, et al. PRB 73, 094442 (2006)

K. Buchanan, et al. PRB 72, 134415 (2005)

11

Two vortices: unique dynamics (o,o)p1p2=+1

(o,i)p1p2= -1

c = chirality

p = polarity

Buchanan, Roy, Grimsditch, Fradin, Guslienko, Bader, and Novosad, Nature Physics 1, 172 (2005).

c1c2= -1100 200 300

0

20

Rea

l Im

peda

nce

Der

ivat

ive

(arb

. uni

ts)

Frequency (MHz)

relative core polarities

determine the dynamics

100 200 300

0

20

single pair

Real

Impe

danc

e D

eriv

ativ

e(a

rb. u

nits)

Frequency (MHz)

||

12

Approaches to Nano Fab . . .

[100][010]

[001]

[100][010]

[001]

[100][010]

[001]

[100]

[010]

13

Chimeric Magnetic Phage ConceptMagnetic Virus Concept

10 - 100 nm range

14

Magnetic Viruses via Capsid Templates

Co2+

Co2+

Co2+

Co2+Co2+

Co2+

Co2+

Co2+

Co2+

Alkaline treatment

C. Liu, et al. JMMM 302 (2006) 47.

T7

15

TEM Images of Magnetic Virus Fabrication

Normal T7 Virus Ghost T7 Virus

200 nm

Alkaline

Treatment

Capsid Proteins

20 nmT7 Capsid Shell with Iron Oxide Inside

Magnetic Virus(NH4 )2 Fe(SO4 )2 + O2 Fe2 O3

pH = 6.5

(NH4 )2 Fe(SO4 )2 + O2 Fe2 O3

pH = 6.5

Biomineralization

Chinmei Liu, Seok-Hwan Chung, April Sutton, Funing Yan, Qiaoling Jin,Axel Hoffmann, Brian Kay, Sam Bader, Lee Makowski, Liaohai Chen

20 nm200 nm 20 nm

16

Research Frontiers in Magnetic Materials at Soft X-ray Synchrotron Radiation FacilitiesJ. Kortright, D. Awschalom, J. Stöhr, S. D. Bader, Y. Idzerda, S. Parkin I. K. Schuller, H.-C. Siegmann,

J. Magn. Magn. Mater. 207 (1999) 7-44

Advances in Nanomagnetism via X-ray Techniques (REVIEW)G. Srajer, L.H. Lewis, S.D. Bader, A. Epstein, C.S. Fadley, E.E. Fullerton, A. Hoffmann,

J.B. Kortright, K.M. Krishnan, S.A. Majetich, T.S. Rahman, C.A. Ross,M.B. Salamon, I.K. Schuller, T.C. Schulthess, J. Z. Sun

J. Magn. Magn. Mater. 307, (2006) 1-31

Magnetism in Low DimensionalityS. D. Bader, Surface Science 500 (2002) 172-188

Colloquium: Opportunities in NanomagnetismS. D. Bader, Rev. Mod. Phys. 78 (2006) 1-15.

Neutron Scattering Studies of Nanomagnetism and Artificially Structured MaterialsM. R. Fitzsimmons, S. D. Bader, J. A. Borchers, G. P. Felcher, J. K. Furdyna, A. Hoffmann, J. B.

Kortright, I. K. Schuller, T. C. Schulthess, S. K. Sinha, M. F. Toney, D. Weller, S. WolfJ. Magn. Magn. Mater. 271 (2004) 103-146

17

Willebrord Snellius

Magneto-OpticsNovel Instrumentation

18

Collaborators

Frank Fradin

Marcos Grimsditch

Axel Hoffmann

Sam Jiang

Valentyn Novosad

John Pearson

Kristen Buchanan

Yongseong Choi

Seok-Huan Chung

Seth Darling

Yi Ji

Paulo Messina

Changyeon Won

Pierre Roy

Volker RoseAnand Bhattacharya

Konstantin Guslienko

Volodymyr Yefremenko

F1 F2

Ve-

Co