Spectroscopic Study of $^{75}$As and $^{139}$La NMR on Layered Structure Ferromagnet LaCoAsO

$^{75}$As and $^{139}$La field-swept NMR spectra were obtained for the novel weakly itinerant ferromagnet LaCoAsO with 2D layered structure above the Curie temperature of 55 K. By analyzing NMR spectra, temperature dependences of Knight shift $K$ and nuclear quadrupole resonance frequency $\nu_Q$ were obtained successfully for each nucleus. We confirmed from the so-called $K$-$\chi$ plots that the macroscopic magnetization of our {LaCoAsO} powder sample is intrinsic and does not contain the contribution from impurity phases. We estimated hyperfine coupling constants from the slope of $K$-$\chi$ plots and compared to that of iron-arsenide superconductor.
Comment: 5 pages, 5 figures, published on J. Phys. Soc. Jpn. at Vol.79, pp.054703 (2010).