nmr-on study of 197 pt ni

2010. 9. 13, HFI/NQI 2010 CERN GENEVA, Switzerland

NMR-ON study of 197PtNi

T. Ohtsubo

S. Ohya, Y. Masamori, T. Izumikawa, (Niigata University)

S. Muto(KEK),

K. Nishimura(Toyama University)


NMR-ON study

• Low-temperature nuclear orientation is useful to get a

polarized unstable nuclei system.

• Nuclear magnetic resonance of oriented nuclei (NMR-ON)

has been widely applied in the study of the

electromagnetic properties of unstable nuclei and

hyperfine interactions of dilute impurities in ferromagnetic

metals.


Hyperfine anomaly

- μ Bhf = ∫ μ (r) Bhf(r)dr = μ Bhf(0)(1+ε )

Magnetic Hyperfine interaction of a nuclear state with magnetic momentdistribution μ (r) in a magnetic hyperfine field with radial distribution Bhf(r)

single-level anomaly(ε ): deviation from the point-dipole interaction(Bohr-Weisskopf effect)

Hyperfine anomaly 1Δ 2

Bpoint charge

Point nucleus

Finite nucleus

orbital

spin

-1Bhf 1

-2Bhf 2


Bohr Weisskopf effect

)2()1()2(

)1(21

)1(

)2(

)2(

)1(

11

11

g

g

s.p.

4

74

4

s.p.

2

52

2s.p. 11NN

S R

Rb

R

Rb

s.p.

4

473

s.p.

2

253

NNL R

Rb

R

Rb

Anomaly factor (single particle model) Anomaly factor including core polarization and mesonic current effects (Fujita Arima)

VNN

S

VNN

S R

Rb

R

Rb

22

38.062.0

mess.p.VN

VN21

VN

4

3

14

31 ls

ss I

I

gg

gg

bs: electron coefficientsR/RN: radial integrals of nucleus(H.H.Stroke and R.J.Blin-Style, PR123(61)1326


NMR in ferromagnetic metal (Fe, Ni,..)

Resonance frequency (magnetic interaction)

00

0

01

BdBd

BKBh

ghf

N

HFA no or very small deference between isotopes

1

0

1

0

2

20

1021

dBd

dBd


Hyperfine anomaly of Yttrium isotopes

frequency [MHz]

91mYFe3

2

1

0

2

1

0

2

1

0

3

2

1

0

2

1

0

310305300295

0.2 T

0.4 T

0.6 T

0.8 T

1.0 T

308

304

300

309.85(4)

0.0 0.4 0.8 1.2

Bext (T)

dνdBext

= 9.8(2) MHz/T

91Y(1/2-), 91mY(9/2+)

g1 d ν 1/dBg2 d ν 2/dB=

9191m = 4.2(8) %


Platinum isotope

Nucleus I T1/2 (N)191Pt 3/2 2.9d 0.494(8)195Pt 1/2 stable +0.60952(6)197Pt 1/2 18.3h 0.51(2)

191PtNi: 0 = 84.349(4) MHzd/dB = 2.449(8) MHz/T

G. Seewald et al.: Phys. Rev. B66, 174401, (2002)


Decay scheme of 197Pt

3/2+1/2+

3/2+

1/2 0

269

77

0

8 %

81 %

11 %

T1/2 = 18.3 h

197

78Pt119

197

79Au118

Q- = 718.9 keV

stable


Sample preparation

• The samples of 197PtNi were prepared by the thermal

neutron irradiation method.

• Thin alloy foils of PtNi (0.1 at. % of the 96 % enriched

196Pt, 2.6m thickness) were irradiated in a reactor at the

Japan Atomic Energy Research Institute.

• After irradiation, the sample was annealed in vacuum for

30min. at 800°C.


3He/4He dilution refrigerator


-ra

y ra

tio(

0°/1

80°)

-ra

y co

unts

asymmetry 1.12(1)

anisotropy0.844(3)

7 mK

0.62

0.68

0.8

1.0×104

197PtNi

58CoNi

3000 6000 9000 sec

Low temperature °Cool down to 7 mK

Low temperature


NMR-ON 197PtNi

～～

～～

0.2 T

0.4 T

0.6 T

frequency (MHz)222 226 230 234

0.69

0.68

0.80

0.79

1.06

1.05

226

228

230

0.0 0.6 0.8Bext (T)

197PtNi

0 = 230.7(2) MHz

d/dB = 6.2(5) MHz/T


NMR-ON study for 191PtNi (Munich Univ.)

[111]

0 = 84.349(4) MHz

d/dB = 2.449(8) MHz/T

G. Seewald et al.: Phys. Rev. B66, 174401, (2002)


Hyperfine anomaly 191197 method 1

I 0(MHz) g-factor197PtNi 1/2 230.7(2) 1.02(4)191PtNi 3/2 84.349(4) 0.329(3)

)%2(131)(

)(191

197

1970

1910197191

Ptg

Ptg

single particle +0.2% Phys. Rev. 123, 1316 (1961)

core polarization -0.6% Nucl. Phys. A254, 513 (1975)


Hyperfine anomaly 191197 method 2

I 0(MHz)d/dB(MHz/T)

197PtNi 1/2 230.7(2) 6.2(5)191PtNi 3/2 84.349(4) 2.449(8)

)%7(71)Pt(

)Pt(191

197

1970

1910197191

NidBd

NidBd

Even though a large error, but consistent with theoretical calculations

single particle +0.2% Phys. Rev. 123, 1316 (1961)

core polarization -0.6% Nucl. Phys. A254, 513 (1975)


Hyperfine anomaly 195197 (same I)

I 0(MHz) g-factor197PtNi 1/2 230.7(2) 1.02(4)195PtNi 1/2 316.0(65)* +1.2190(1)

)%5(151)(

)(195

197

1970

1950197195

Ptg

Ptg

If we use the known magnetic moment of 197Pt, the hyperfine anomaly between 195Pt and 197Pt is very large, even though they have same spin-parity. The known magnetic moment of 197Pt should be wrong.

*M. Kontani and J. Itoh: J. Phys. Soc. Japan 22 345, (1967)


Magnetic moment of 197Pt

• The known value of 197Pt (0.51(2) N) was measured by the atomic beam method. It was reported by Y.W. Chan, et al. in Bulletin of the American Physical Society 13, No.6, 895 CE14(1968), but it was not published.

• Using the known hyperfine field of 195PtNi (34(7) T) and the present result, the magnetic moment of 197Pt can be deduced as:

(197Pt: 1/2) = 0.45(1) N.

where we ignore the hyperfine anomaly 195197 because they have same spin-parity. Using this value, the hyperfine anomaly 191197 can be deduced:

191197 = 0(2) %.


Summary

• We observed the NMR-ON spectra of 197PtNi. • Comparing with the result of 191PtNi, we deduce

the hyperfine anomaly 191197 = +13(2)%. This value is too large. The known magnetic moment of 197Pt should be wrong.

• Using the known Bhf(195PtNi), the magnetic moment of 197Pt is deduced as: (197Pt) = 0.45(1) N.

• Using this new value, the hyperfine anomaly is 191197 = 0(2) %.


Low temperature nuclear orientation()

Ge detector

population population

γ -ray angular distribution

rf frequency

γ-r

ayde

tect

ion

hν =Δ E

transition

resonance


Low temperature nuclear orientation()

H= -μ ・B= -gμ N I・B= -gμ N B0Iz

Em = <m|H | m>

= -gμ N B0m

B0

I = 5 case

energy

m = -5

m = +5

Magnetic Interaction

B = 0 B = 0

magnetic quantum number

μ

.

.

.

Population am ∝ e-Em/kT

low temperaturehigh field

Polarization(Orientation)

Boltzmann ditribution

Zeeman split


External field dependence of 91YFe and 91mYFe

0.0

-0.2

-0.4

1.21.00.80.60.40.20.0

300

304

308

external magnetic field (T)

reso

nanc

efr

eque

ncy

(MH

z)

91mYFe

deviation

f0 = 309.87(5) MHzdf/dB = -9.89(11) MHz/T

74

72

70

68

663.02.52.01.51.00.50.0

4

0

-4

x10-2

external magnetic field (T)

reso

nanc

efr

eque

ncy

(MH

z)

f0 = 73.55(2) MHzdf/dB = -2.49(2) MHz/T

deviation

91YFe

nmr-on study of 197 pt ni

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