Nuclear Magnetic Resonance of ^{169}Tm (Enhanced) and ^{31}P in TmPO_4
Abstract
The enhanced nuclear magnetic resonance (n.m.r.) spectrum of ^{169}Tm (I = 1/2 in the tetragonal compound TmPO_4 has been measured from 1.6 K to 30 K. It is highly anisotropic, with γ/2π = 11.34 and 276 MHzT^{1}, parallel and perpendicular to the caxis respectively, at the lowest temperatures. The corresponding values of the Van Vleck electronic susceptibility per ion are 0.0231 and 0.805 μ_B T^{1}. Above 4 K the values of γ/2π become temperature dependent as excited levels become populated, and the results are discussed in the light of a crystal field calculation of the energy levels and wave functions. The n.m.r. spectrum of ^{31}P (I = 1/2) is shown to exhibit an anisotropic paramagnetic shift, mainly dipolar in origin, exactly proportional to the electronic susceptibility of the Tm^{3+} ions, and this is used to extrapolate the measurement of γ for ^{169}Tm up to 64 K in the perpendicular direction. A simple calculation of the direct process for spinlattice relaxation shows that this is orders of magnitude too slow to account for the observed relaxation rates, which must be ascribed to the presence of paramagnetic impurities.
 Publication:

Proceedings of the Royal Society of London Series A
 Pub Date:
 May 1983
 DOI:
 10.1098/rspa.1983.0051
 Bibcode:
 1983RSPSA.387...75B