Higher-order contribution and temperature dependence of the magnetic anisotropy in ultrathin films (invited)

The pseudomorphic growth of ultrathin films produces artificial structures, and with it anomalously large magnetic anisotropy energies (MAEs). Second- and fourth-order MAEs K-2,K-4 can be measured and analyzed. To understand the continuous (steplike) rotation of M in a spin reorientation transition (SRT), K-4<0(K-4>0) is necessary. By means of ferromagnetic resonance measurements we show that for fct Ni/Cu(001) the SRT is of second order. It is important to measure the ''surface'' and ''volume'' contribution for all MAE contributions K-2,K-4,... as a function of temperature. These results are compared with T = 0 K first principle electronic structure calculations. (C) 1997 American Institute of Physics.