Strain-induced tetragonal distortions in epitaxial Ni-films grown on Cu(001)

The structural and magnetic properties of thin Ni films epitaxially grown o n Cu(001) substrates have been investigated using ab-initio local-spin-dens ity calculations in the generalized gradient approximation. We show that th e lattice mismatch at the Ni-Cu interface induces a tetragonal distortion o f the Ni-films of about 6%, superposed at the free surface by an inward rel axation of the Ni top-layer which is slightly larger than in bulk fee Ni(00 1). The magnetic moments of the Ni atoms are enhanced at the free surface, but reduced at the Ni-Cu interface relative to the value in bulk Ni. The ef fect of the surfactant Cu layer is examined and it is shown that this effec t can account for the existing discrepancies between calculated and measure d structural features of thin Ni films.