Local and long-range realizations of a spin-reorientation surface phase transition

Abstract

The spin reorientation transition of an ultrathin film from perpendicular to in-plane magnetization is driven by a competition between dipole and anisotropy energies. In situ measurements of the magnetic susceptibility of Fe/2 ML Ni/W(110) films as a function of Fe coverage, made as the films are deposited at constant temperature, show two clear peaks; one at the long-range and one at the local realization of the transition. In the long-range realization, the susceptibility probes the striped domain pattern that is formed in response to the balance of energetics on a mesoscopic scale. Here the reorientation transition occurs at a non-integer layer thickness. In the local realization, the susceptibility probes the response of small islands with in-plane anisotropy in the 3rd atomic Fe layer that are grown on the 2nd atomic Fe layer, which has perpendicular anisotropy. It is a response to the local finite-size, metastable energetics due to discrete steps in thickness. An excellent quantitative description of the susceptibility data is obtained when both local and long-range aspects of the spin reorientation transition are included.

Comparison of dynamical and equilibrium surface spin reorientations: Inferences on the nature of the phase transitions in the presence of dipole interactions

“…This model is developed in ref. (28) and shown to give an excellent quantitative description of the first peak in the experimentally measured susceptibility.…”

“…Similar measurements are analyzed quantitatively in ref. (28). The two peaks are the magnetic response at the local (near 1 ML) and the global (near 3 ML) realizations of the same reorientation transition.…”

“…Eq. ( 7), ( 9) and ( 11) provide an excellent quantitative description of the peak in the measured susceptibility at higher deposition 28 . The peak at lower deposition in fig.…”

“…Magnetic microscopy experiments have been effective in providing evidence of changes in the order of the domain pattern 25,26 , but temporal limitations of the imaging technique make it difficult to approach the critical region and characterize the transitions. Measurements of the magnetic susceptibility can be made throughout the critical region of the spin-reorientation transition 15,27,28 , but there is no evidence 28,29 of a magnetic phase transition from the perpendicular domain state or to the in-plane magnetized state, as would normally be indicated by a divergence in the appropriate component of the magnetic susceptibility 30 . A similar problem is encountered at the thermal transition from the perpendicular domain phase directly to the paramagnetic phase, where domain wall fluctuations make imaging difficult 31 and demagnetization effects render magnetic measurements ambiguous or insensitive 27,32 .…”

Two-dimensional percolation transition at finite temperature: Phase boundary for in-plane magnetism in films with two atomic layers of Fe on W(110)

“…The error in the calibration is 5%. A previous study has shown that the flux calibration is linear in ion current, and stable in time over the time periods required to grow films while the magnetic susceptibility is being measured in real time 32 . For this type of measurement, the uncertainty along the deposition axis derived linearly from the deposition time is entirely accounted for by the uncertainty in the original flux calibration using AES.…”