Experimental study of the magnetic critical behavior of the Ni(001) and Ni(110) surfaces (invited)

Abstract

Dedicated to Professor S. Methfessel, upon the occasion of his sixtieth birthday. The critical behavior of the surface magnetization of atomically clean Ni surfaces has been studied by spin polarized low energy electron diffraction. The critical exponent β1 of the order parameter—surface magnetization—is determined from the temperature dependence of the magnetic exchange scattering asymmetry for the specularly reflected beam at various angles of incidence and kinetic energies of the primary beam. For the (001) surface we find β1=0.8 and for the (110) surface β1=0.79, with a statistical uncertainty of ±0.02. The difference in the critical exponent for the two surfaces is thus within experimental accuracy. This indicates that the larger surface relaxation of the (110) surface does not significantly influence the value of the critical exponent β1 in the temperature range 0.002≲1−T/TC≲0.1. The experimental values of the critical exponent β1 are slightly smaller than the predictions of ε-expansion calculations for the Heisenberg model (n=d=3), which lie in the range (0.81–0.88).