Critical behavior of strained epitaxial Gd films:<i>In situ</i>ac-susceptibility measurements in UHV

Abstract

300-\AA{} Gd films grown on W(110) under UHV conditions have been investigated Iin situR by ac-susceptibility measurements above and below ${\mathit{T}}_{\mathit{c}}$. A sharp peak of ${\mathrm{\ensuremath{\chi}}}_{\mathrm{ac}}$=230 is observed. To our knowledge, this is the largest and sharpest (2\ensuremath{\sigma}=1 K) cusp measured for a rare-earth ferromagnet. No domain-wall signal is superimposed upon the divergence of the paramagnetic susceptibility. At ${\mathit{T}}_{\mathit{c}}^{+}$ we find \ensuremath{\chi}=${\mathrm{\ensuremath{\chi}}}_{0}$${\mathit{t}}^{\mathrm{\ensuremath{-}}\ensuremath{\gamma}}$ with \ensuremath{\gamma}=1.235(25). This is clear evidence for a three-dimensional Ising-like behavior above ${\mathit{T}}_{\mathit{c}}$. The sharpness and peak position of \ensuremath{\chi}(T) change, depending on the annealing temperature. Simultaneously, a change in the LEED pattern is observed.