It has been found that in highly anisometric ribbon-shaped Fe particles with nanoscale dimensions that the magnetization decreases with temperature markedly faster than in bulk bcc Fe. This anomalous dependence, which becomes more remarkable as the length-to-cross section ratio increases, arises from the elongated shape of the particles. The analytical approximation performed on the thermal spectrum of magnons, compatible with the sample dimensions, unravels the correlated influences of shape and size on the thermal decreasing rate of magnetization.

• Received 29 September 2003

DOI:https://doi.org/10.1103/PhysRevB.69.012403