Efficient spin-polarized electron injection is a prerequisite for the development of semiconductor-based spintronic devices. Several recent experimental studies have reported successful electrical spin injection from ferromagnetic metals into III-V semiconductor light emitting diodes (LEDs) using a variety of tunnel barriers. However, further improvement requires a detailed understanding of interface magnetic properties.@footnote 1@ In this study, we have measured the reversal process of the Fe interface layer magnetization in Fe/AlGaAs heterostructures using magnetization-induced second harmonic generation (MSHG), and compared it with the bulk magnetization as obtained from magneto-optic Kerr effect (MOKE).@footnote 2@ The switching characteristics are distinctly different - single step switching occurs at the interface layer, while two-jump switching occurs in the bulk Fe for the magnetic field orientations employed. The different switching processes lead to a deviation angle of 40-85o between interface and bulk magnetization. This behavior may result from reduced exchange interaction in the direction normal to the interface and different magnetic anisotropies at the heterojunction. To study the magnetization dynamics at the interface, we use time-resolved MSHG to investigate the coherent magnetization precession. The results are directly compared with the bulk spin precession as obtained from time-resolved MOKE.@footnoe 3@ The different switching characteristics are further revealed in the precession dynamics at low fields. The field dependence of precession frequency provides a quantitative analysis of magnetic anisotropy and magnetostatic energy of the interface layer. @FootnoteText@ @footnote 1@J. M. D. Teresa et al., Science 286, 507 (1999); B. T. Jonker, Proc. IEEE 91, 727 (2003). @footnote 2@H.B. Zhao et al., Phys. Rev. Lett. 95, 137202 (2005). @footnote 3@H.B. Zhao et al., Appl. Phys. Lett. 86, 152512 (2005).