Start Over

Magnetic moments of bare and benzene-capped cobalt clusters.

Authors :: Knickelbein, Mark B.
Source :: Journal of Chemical Physics; 7/28/2006, Vol. 125 Issue 4, p044308, 7p, 5 Graphs
Publication Year :: 2006
Abstract: Magnetic moments of bare cobalt clusters Co<subscript>n</subscript> (n=7–32) and benzene-capped cobalt clusters Co<subscript>n</subscript>(bz)<subscript>m</subscript> have been measured at temperatures ranging from 54 to 150 K using a molecular beam deflection method. It was observed that Co<subscript>12–32</subscript> produced at temperatures greater than ∼100 K display high-field-seeking behavior at all temperatures in the range investigated, indicating that they are superparamagnetic species. At temperatures below ∼100 K, the field-on beam profiles of Co<subscript>7–11</subscript> and some larger clusters displayed substantial symmetric broadening, indicating that some fraction of the clusters in the beam were no longer superparamagnetic, but rather were in a blocked (locked-moment) state. In the superparamagnetic regime (T=150 K) Co<subscript>n</subscript> clusters in the n=7–32 size range were found to possess per-atom moments ranging from 1.96±0.04μ<subscript>b</subscript>(Co<subscript>24</subscript>) to 2.53±0.04μ<subscript>b</subscript>(Co<subscript>16</subscript>), significantly above the bulk value of 1.72μ<subscript>b</subscript>. Locked-moment isomers were found to display moments of ∼1μ<subscript>b</subscript> per atom. Cobalt clusters containing a layer of adsorbed benzene molecules were found to possess significantly lower moments per cobalt atom than the corresponding bare cobalt clusters. [ABSTRACT FROM AUTHOR]