Date/Time
Date(s) - 14/09/2011
3:20 pm - 4:20 pm

Title: Competing Anisotropies in a 2D Ferromagnetic Phase Transition

Speaker: Dr. David Venus – McMaster University

Institute: McMaster University

Location: ABB 102

Description:

Ultrathin magnetic films (a few atomic layers in thickness) provide an opportunity to investigate phase transitions in a truly two dimensional system. Since these films often have incomplete atomic layers, they are not entirely uniform, but contain structural defects. An important issue is how these inhomogeneities affect the transition between the ferromagnetic and paramagnetic states. Recent measurements of the transverse (hard axis) susceptibility of Fe/W(110) films in the thickness range of 1.6 ML to 2.4 ML have revealed an unexpected, sharply peaked signal whose amplitude and peak temperature depend systematically on the layer completion of the film. These measurements are naturally described by the presence of magnetic anisotropies associated with partially complete atomic layers. The Harris criterion is used to relate these
results to previously reported findings on the variation of the critical exponent of the susceptibility with thickness in this same film system.