Resonance like enhancement of magneto-optic Kerr effects (MOKEs) have been attributed to numerous effects, one of them being plasma resonance of free charge carriers, which is analytically and numerically investigated here. Analytical expressions for frequency dependent enhancement of MOKE are obtained in the general framework of the Drude model, which are then applied to well known expressions describing MOKE. The derived expressions are numerically tested for various optical constants. It is known that for certain materials, the resonance like enhancements in the Kerr spectrum occur in the near vicinity of Re[εxx]=1, which is generally near the plasma edge. This is seen to be true when the plasma frequency ωp is greater in magnitude as compared to the cyclotron frequency ωc, i.e., if ωp≫ωc, whereas in the event of a large reflection edge split, i.e., if ωp∼ωc the resonance like peaks will occur near Re[ε+.ε−]≈1, which is a relatively more general condition as compared to Re[εxx]=1. Second, we see through model calculations that the spectral proximity of the MOKE resonance peak to the plasma edge is also subject to the magnitude of the background dielectric constant. Results are explained analytically and numerically. Good agreement is obtained between the expressions derived here and the numerically observed occurrence of resonance like peaks in the Kerr spectrum.
Journal of Applied Physics
J. Appl. Phys. 92, 5401 (2002)