Interface Magnetization Reversal and Anisotropy in $\mathrm{Fe}/\mathrm{AlGaAs}(001)$

The reversal process of the Fe interface layer magnetization in $\mathrm{Fe}/\mathrm{AlGaAs}$ heterostructures is measured directly using magnetization-induced second-harmonic generation, and is compared with the reversal of the bulk magnetization as obtained from magneto-optic Kerr effect. The switching characteristics are distinctly different due to interface-derived anisotropy—single step switching occurs at the interface layer, while two-jump switching occurs in the bulk Fe for the magnetic field orientations employed. The angle between the interface and bulk magnetization may be as large as 40–85 degrees. Such interface switching will dominate the behavior of nanoscale structures.

Figure 1

Longitudinal MSHG, (a)–(d), and MOKE, (e)–(h), $M\mathrm{\text{−}}H$ loops from 10 nm Fe film with the field applied along the principal crystallographic axes $[110]$, $[1\mathrm{\text{−}}10]$, $[010]$, and $[100]$, respectively. The squares (triangles) indicate increasing (decreasing) magnetic field. The coercive fields are listed in each panel.

Figure 2

(a) Experimental configuration, (b) $M\mathrm{\text{−}}H$ loop for one-jump switching; (c) $M\mathrm{\text{−}}H$ loop for two-jump switching, and (d) sequence of the two-jump process. The numbers relate the steps in the sequence to the corresponding feature in the $M\mathrm{\text{−}}H$ loop.

Figure 3

Longitudinal MSHG, (a) and (b), and MOKE, (c) and (d), $M\mathrm{\text{−}}H$ loops from the 50 nm Fe film capped with a 5 nm Cr layer with the field applied along the hard-easy $[110]$ and hard-hard $[1\mathrm{\text{−}}10]$ axes, respectively. The squares (triangles) indicate increasing (decreasing) magnetic field.