Different scenarios for the in-plane spin reorientation transition in Fe(110) films on W(110)

We investigated the spin reorientation transition during the growth of Fe(110) films on W(110) at 250 °C using the in situ nuclear resonant scattering of x rays. The measurements as a function of the grazing incidence angle demonstrated that the spin reorientation proceeds via an intermediate, noncollinear magnetic state, and with increasing thickness, the magnetization reorientation from the [1$\overline{1}$0] to the [001] direction is activated at the film surface and completed at the Fe/W interface. Furthermore, as the temperature was decreased from 250 °C to 160 °C, the temperature-driven spin reorientation transition (SRT) between the [001] and [1$\overline{1}$0] directions was observed with a similar noncollinear transient magnetic state. The thickness-temperature SRT phase diagram was schematically drawn.

Figure 1

The NRS time spectra for the 6-nm-thick Fe film on a tungsten substrate simulated for the three grazing incidence angles θ, assuming (a) homogenous in-plane magnetization parallel to the $k$ vector of the x-ray beam, (b) in-plane noncollinear structure composed of the top 3-nm-thick sublayer with the magnetization parallel to the $k$ vector of the x-ray beam and the bottom 3-nm-thick sublayer with an orthogonal magnetization orientation, and (c) homogenous in-plane magnetization perpendicular to the $k$ vector of the x-ray beam. The intensity axis (not shown) is displayed in a logarithmic scale.

Figure 2

The NRS time spectra measured for the grazing incidence angle of θ = 0.25° during the thickness-induced SRT at 250 °C are shown for the selected Fe thicknesses $d$ (given in nm). The red line represents the fits obtained using the model with 16 sublayers. The inset shows the fitted time spectra recorded during the thickness-driven SRT process ($d$ = 6.6 nm) for the grazing incidence angles of θ = 0.1° and θ = 0.35°.

Figure 3

The evolution of the spin structure during the thickness-driven SRT at 250 °C derived from the NRS data is shown schematically as a function of the Fe thickness (indicated at the bottom in nm). The arrows represent the sublayer magnetizations. The angles ${\phi }_N$ between the magnetization vector and the [1$\overline{1}$0] direction are given in degrees.

Figure 4

Fitted NRS time spectra collected for the 6.9-nm-thick Fe film during the following temperature cycle: 250 °C → 160 °C → 250 °C, from top to bottom, are shown for the grazing incidence angle of θ = 0.25°.

Figure 5

The evolution of the magnetic structure derived from the numerical analysis of the NRS time spectra collected during the temperature cycle of 250 °C → 160 °C → 250 °C for the 6.9-nm-thick Fe film on W(110). The arrows represent the sublayer magnetizations. The angles ${\phi }_N$ between the magnetization vector and the [1$\overline{1}$0] direction are given in degrees.

Figure 6

The thickness vs temperature phase diagram of the SRT process in the Fe(110) films grown at 250 °C derived from the thickness and temperature-dependent NRS studies.