Hyperfine Interactions of ¹²B Implanted in Ferromagnetic Nickel

Abstract

Temperature dependences of hyperfine interactions of 12 B implanted in Ni were investigated in the temperature range of 6 K–730 K by the NMR method with use of polarized 12 B produced in a nuclear reaction and the asymmetric β decay. Two kinds of hyperfine fields with different signs were observed ( B hf + =+4.161 ±0.022 kG and B hf - = -1.611 ±0.021 kG at 6 K), which indicated that the implanted 12 B were trapped in two different sites (S + and S - , respectively). The spin-lattice relaxation times T 1 and the population rates at the two sites were studied. Near the Curie temperature, an effect of critical slowing-down of the spin-spin correlation was observed as steep variation of T 1 . The behavior of local field around T C was also studied by varying the external field. Results of these experiments near T C indicate itinerant nature of the electron-spin structure in nickel.