Finite-temperature surface properties of itinerant-electron ferromagnets

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Abstract
Magnetic properties of metallic surfaces at finite temperatures are discussed by using the single-site spin-fluctuation theory in which the effects of spin fluctuations both at the surface and in the bulk are taken into account on the same footing by means of the static functional-integral method. The temperature dependence of the layer-by-layer magnetic moments on the first time layers is calculated numerically for the semi-infinite simple cubic lattice with the (100) surface. Model calculations using the parameters appropriate to Ni show that the magnetic order at the 'clean' surface persists above the bulk Curie temperature, TCb, and that the amplitudes of local spin fluctuations on the first few layers are significantly enhanced near TCb compared with that in the bulk. Calculated results are compared with those obtained in the mean-field theory for the semi-infinite simple cubic Ising model and they are discussed with reference to relevant experimental data.