A new 27Al NMR has been observed in the paramagnetic state of GdAl2 between 350° and 575°K. The 27Al NMR linewidth δH was found to be strongly temperature-dependent. Data are presented which suggest that the previously reported 27Al NMR in GdAl2 is probably due to a small amount of some other Gd–Al compound. The 27Al Knight shift is temperature-dependent, varying from about −6% to −3% between 350° and 575°K, respectively. The temperature-dependent part of the Knight shift obeys a Curie-Weiss law, i.e., K(T) α (T−θ)−1, with θ≃150°K. The temperature-independent part of the Knight shift is consistent with the value measured for the nonmagnetic isomorph LaAl2. Extrapolating the Knight shift data to 300°K and combining K(300) with the room-temperature susceptibility χ(300) yields an effective 27Al hyperfine field Hhf≃−6.8 kOe per Bohr magneton. An 27Al hyperfine field in the ferromagnetic state is thus calculated to be 27H≃−46 kOe in good agreement with experiment. The s-f exchange energy is calculated to be Jsf=−0.13 eV. The 27Al nuclear quadrupolar coupling constant was measured to be (e2qQ/h)≃4.27 Mc/sec.
No takes yet. Share an insight, caveat, or question.
Jones et al. (1966) studied this question.