What happens at the temperature-dependent magnetic order-disorder transition in Fe/Cu(001)?

The magnetic order-disorder transition induced by a temperature-driven structural transformation from tetragonal to cubic at about 4 ML Fe/Cu(001) was studied in detail by means of ferromagnetic resonance in situ. From the unusual temperature dependence of the magnetisation, spin fluctuations and magnetic anisotropy energy we find that the structural transformation occurs over the full layer thickness and is not limited to a surface layer. Face-centred tetragonal patches decrease in volume and are completely transformed to fee Fe above T* approximate to 320 K. A positive and large volume and surface anisotropy was determined as well as the temperature dependence of the uniaxial anisotropy for the tetragonally distorted thickness range (d less than or equal to 4 ML).