Temperature dependent studies of capped magnetic nanowires using XMCD

Abstract

Aligned cobalt nanowires, 1, 2, and 3 atoms wide, were grown on platinum (997) surfaces under UHV conditions and capped with five monolayers of gold. X-ray magnetic circular dichroism (XMCD) measurements were performed at the L 2,3 edges of Co. Element specific magnetic hysteresis loops were measured as a function of temperature and coercivities were extracted. The easy axis of magnetization was confirmed to be perpendicular to the (111) terrace for all samples. The temperature dependence of the coercivity, which varies by an order-of-magnitude over a 150 K temperature range for the 1-atom-wide wire, was found to be well described by the Gaunt "strong" domain wall pinning model for all three wires. The observation that capping increases the Curie temperature of the 1-atom-wide nanowire by at least 270 K, together with the strong temperature dependence of the coercivity and the perpendicular magnetic anisotropy, may have important implications for the technological application of low dimensional, nanoscale magnetic materials.