Evidence for domain condensation near the ferromagnetic to paramagnetic transition in perpendicularly magnetized, ultrathin Fe/2 ML Ni/W[110] films

Ultrathin, fcc Fe/2 ML Ni(111) films were grown on a W(ll0) substrate in UHV by electron beam evaporation. Fe films less than 2.2 ML thick posses a perpendicular moment that does not reorient to an in-plane easy axis below Tc, the temperature of the ferromagnetic to paramagnetic transition. The magnetic susceptibility of the fllms was measured as a function of temperature using the polar Kerr effect. The real part of the susceptibility is large, peaking at well above 100 SI units, and exhibits a simple exponentJal decay over a range of several tens of Kelvin above the temperature TREM where the remanent magnetization disappears. This behavior of the susceptibility is in agreement with that expected from the perpendicularly magnetiaed domnin structure usually identified as a precursor to a spin reorientation transition. No signature of Tc is found in the susceptibility.