Nuclear Magnetic Resonance inαandβManganese

Abstract

JULY 15, I960 Table I. The room temperature values of k for the d 1 andd 3 metals in percent. a ' nnn-= 3 = 4 = 5 d> 21 Sc: 0. 57 La: 0 24 .63 & i 2 3 V: 4 lNb: 7J Ta: d 3 0.58 ; 0.87 : 1.1 a W. D. Knight, reference 1. b L. H. Bennett and J. I. Budnick, Bull. Am. Phys. Soc. j>, 242 (1960).ever, the large increase as one proceeds from 3d 1 to 3d 3 or M 1 to 5d 3 is not expected. 5 We suggest that this results from the enhanced s -electron polarization produced by the s-d exchange interaction.It is noteworthy that the linewidths of Sc, V, Nb, and La are all considerably larger than the direct nuclear dipole-dipole interaction would allow. Since all these elements have single isotopes of overwhelming abundance any indirectThe properties of the nuclear magnetic resonance (NMR) of Mn 55 in a and /3 Mn have been investigated as a function of field and temperature. 1 A very broad asymmetric NMR (67/" 2 50 oe) was observed in aMn at 295°K. The center of gravity of the resonance corresponds to a negative Knight shift (k) (see Table I). Since there are four magnetically inequivalent sites, 2 it was first thought that the line shape was the result of superposition of several resonances. However, a negligible field dependence was observed for the shape of the line. The a phase is known to have an antiferromagnetic transition at 95°K. 3 Correspondingly, no resonance was visible at 77°K and 20.2°K in the randomly oriented powdered sample.In /3Mn only a single resonance line was found, although there occur two physically inequivalent sites. The value of k observed as a function of exchange interaction would not produce line broadening. 6 The field independence of the linewidth and the line shapes exclude both quadrupolar and anisotropic magnetic contributions. These facts, combined with the Gaussian shape and the temperature independence of the linewidth, indicate a pseudodipolar origin for the observed line shapes. . This author reports a Curie-Weiss behavior with the Curie constant indicating an effective magnetic moment of one-half of a Bohr magneton. 3 R. M, Bozorth (private communication). 4 K. Yosida, Phys. Rev. 106, 893 (1957). 5 One must of course allow for the fact that all of the 4/ elements occur between La and Ta. 6 M. A. Ruderman and C" Kittel, PhySo Rev. 96, 99 (1954). Table Io The temperature dependence of the Knight shift in/3Mn as observed at 14.245 Mc/sec. An error of ± 0. 02 % exists in each of the values given, k was determined with respect to the Mn 55 NMR in a saturated solution of LiMn0 4 and in KMn0 4 . The field for resonance in the two solutions is identical to one part in 10 5 . No chemical shifts have been reported for Mn 55 in the literature. T(°K) k(%) 1.8 -0.11 4o2 -0.11 20o2 -0.12 77 -0.13 190 -0.13 295 -0.13 NUCLEAR MAGNETIC RESONANCE IN a AND 0 MANGANESE

NMR and dc susceptibility studies ofNaVGe2O6

“…In this case, T −1 1 (T ) is given by Equation (28), and ∆ corresponds to the gap in the magnon spectrum. Such a gap is usually attributed to an easy-axis single-ion magnetic anisotropy term in the Hamiltonian, of the form D i S i,z S i,z with D < 0 [26].…”

Nuclear and Electron Spin Resonance

“…Further observations of shifts in inorganic compounds have been made for the fluorine resonance in FeF2 (191) and in KMnF 3 (192), the cobalt resonance in CoO (193), and rare earth nuclei in various intermetallic com pounds (194). In the latter case the spin density is carried to the nuclei by an exchange interaction between 4f electrons and conduction electrons; the exchange energy is negative.…”

The general physical properties of manganese metal

“…34,48 The signal appears to be caused solely by Site-I atoms. Calculations indicate that the effect from Site-II atoms is unobservable because of the presence of an inhomogeneous quadrupole interaction that is five times greater at Site II than at Site I.…”