High Curie Temperature and Possible Canted Magnetism in Free Gd Clusters

Abstract

The magnetic properties of free ${\mathrm{Gd}}_{N}$ clusters ( $N\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}13$, 21, and 22) have been measured between 90 and 600 K in a Stern-Gerlach experiment. ${\mathrm{Gd}}_{13}$ and ${\mathrm{Gd}}_{21}$ are found to be superparamagnetic (SP) whereas ${\mathrm{Gd}}_{22}$ is not. Within the SP model, the magnetic moment per atom at 100 K is $5.4{\ensuremath{\mu}}_{B}$ for ${\mathrm{Gd}}_{13}$ and $5{\ensuremath{\mu}}_{B}$ for ${\mathrm{Gd}}_{21}$, lower than the bulk value, $7.55{\ensuremath{\mu}}_{B}$. We measure Curie temperatures of $420\ifmmode\pm\else\textpm\fi{}20\mathrm{K}$ for ${\mathrm{Gd}}_{21}$ and over 500 K for ${\mathrm{Gd}}_{13}$, significantly higher than 293 K, the bulk value. A canted magnetic moment model is compatible with the experimental data.