Thickness-dependent dynamic hysteresis scaling behavior in epitaxial Fe/GaAs(001) and Fe/InAs(001) ultrathin films

The dynamic hysteresis scaling behavior in epitaxial Fe/GaAs(001) and Fe/In As(001) thin films (thickness range 7.3-150 Angstrom) has been investigated as a function of Fe film thickness in the field sweep rate range 0.005-100 0 kOe/s using the magneto-optic Kerr effect. The hysteresis loop area A fol lows the scaling relation A proportional to (dH/dt)(alpha). We find two dis tinct dynamic regimes: the low dynamic regime in the sweep rate range 0.005 -250 kOe/s, and the high dynamic regime beyond 250 kOe/s. There is a marked increase in alpha between the low and high dynamic regimes which we attrib ute to the dominant reversal mechanism changing from domain wall motion to nucleation. In the low dynamic regime alpha is a decreasing function of Fe film thickness, and this behavior is attributed to the effect of interface- induced pinning. (C) 2001 American Institute of Physics.