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NMR-ON study of 197 Pt Ni

NMR-ON study of 197 Pt Ni. 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.

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NMR-ON study of 197 Pt Ni

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  1. NMR-ON study of 197PtNi T. Ohtsubo S. Ohya, Y. Masamori, T. Izumikawa, (Niigata University) S. Muto(KEK), K. Nishimura(Toyama University)

  2. 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.

  3. Hyperfine anomaly

  4. ( 1 ) ( 2 ) ( 1 ) g + e n 1 1 2 ( 1 ) ( 2 ) = + D = » + e - e 1 1 ( 2 ) ( 1 ) ( 2 ) g + e n 1 Bohr Weisskopf effect Anomaly factor (single particle model) Anomaly factor including core polarization and mesonic current effects (Fujita Arima) bs: electron coefficients R/RN: radial integrals of nucleus (H.H.Stroke and R.J.Blin-Style, PR123(61)1326

  5. NMR in ferromagnetic metal (Fe, Ni,..) Resonance frequency (magnetic interaction) HFA no or very small deference between isotopes

  6. Hyperfine anomaly of Yttrium isotopes 91Y(1/2-), 91mY(9/2+) g d / d B ν 1 1 = g d / d B ν 2 2 91D91m = -4.2(8) %

  7. Platinum isotope Nucleus IpT1/2m (mN) 191Pt 3/2- 2.9d -0.494(8) 195Pt 1/2- stable +0.60952(6) 197Pt 1/2- 18.3h 0.51(2) 191PtNi: n0 = 84.349(4) MHz dn/dB = -2.449(8) MHz/T G. Seewald et al.: Phys. Rev. B66, 174401, (2002)

  8. Decay scheme of 197Pt

  9. Sample preparation • The samples of 197PtNiwere prepared by the thermal neutron irradiation method. • Thin alloy foils of PtNi (0.1 at. % of the 96 % enriched 196Pt, 2.6mm 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.

  10. 3He/4He dilution refrigerator

  11. Cool down to 7 mK 197PtNi 0.68 Low temperature asymmetry 1.12(1) ° b-ray ratio(0°/180°) 0.62 1.0 ×104 anisotropy 0.844(3) 58CoNi g-ray counts Low temperature 7 mK 0.8 3000 6000 9000 sec

  12. NMR-ON 197PtNi n0 = 230.7(2) MHz dn/dB = -6.2(5) MHz/T

  13. NMR-ON study for 191PtNi (Munich Univ.) G. Seewald et al.: Phys. Rev. B66, 174401, (2002) [111] n0 = 84.349(4) MHz dn/dB = -2.449(8) MHz/T

  14. Hyperfine anomaly 191D197 method 1 Ipn0(MHz) g-factor 197PtNi 1/2- 230.7(2) 1.02(4) 191PtNi 3/2 - 84.349(4) 0.329(3) single particle +0.2% Phys. Rev. 123, 1316 (1961) core polarization -0.6% Nucl. Phys. A254, 513 (1975)

  15. Hyperfine anomaly 191D197 method 2 Ipn0(MHz) dn/dB(MHz/T) 197PtNi 1/2- 230.7(2) -6.2(5) 191PtNi 3/2- 84.349(4) -2.449(8) single particle +0.2% Phys. Rev. 123, 1316 (1961) core polarization -0.6% Nucl. Phys. A254, 513 (1975) Even though a large error, but consistent with theoretical calculations

  16. Hyperfine anomaly 195D197 (same Ip) Ipn0(MHz) g-factor 197PtNi 1/2- 230.7(2) 1.02(4) 195PtNi 1/2 - 316.0(65)* +1.2190(1) *M. Kontani and J. Itoh: J. Phys. Soc. Japan 22 345, (1967) 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.

  17. Magnetic moment of 197Pt • The known value of 197Pt (0.51(2) mN) 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: m(197Pt: 1/2-) = 0.45(1) mN. where we ignore the hyperfine anomaly 195D197 because they have same spin-parity. Using this value, the hyperfine anomaly 191D197 can be deduced: 191D197 = 0(2) %.

  18. Summary • We observed the NMR-ON spectra of 197PtNi. • Comparing with the result of 191PtNi, we deduce the hyperfine anomaly 191D197 = +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: m(197Pt) = 0.45(1) mN. • Using this new value, the hyperfine anomaly is 191D197 = 0(2) %.

  19. Low temperature nuclear orientation(NMR-ON)

  20. Low temperature nuclear orientation(NMR-ON)

  21. External field dependence of 91YFe and 91mYFe

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