Bloch’s law for epitaxial ultrathin dot arrays with uniaxial magnetic anisotropy

Abstract

Dot arrays with dots of well-defined circular shape have been patterned from epitaxial Fe films on GaAs(001). Magnetization reversal and temperature dependence of the spontaneous magnetization were studied by superconducting quantum interference device magnetometry, an alternating gradient magnetometer and the magneto-optical Kerr effect. It was observed that Bloch T3/2 law is valid for all dot diameters. The spin wave parameter B increases with a decrease in dot diameter by a factor of 4, which reduces the magnetization at room temperature by about 25% compared to its value at 10 K for the smallest dots. From this observation it is concluded that additional excitation modes are present in the spin system.