X-ray magneto-optic Kerr effect studies of spring magnet heterostructures

The complex 3-dimensional magnetization reversal behavior of Sm-Co/Fe excha nge spring films is used to test the sensitivity of different resonant soft X-ray magneto-optical Kerr effect (MOKE) measurements to changes in longit udinal and transverse moments within the soft Fe layer and to changes in th ese moments in depth within the Fe layer, As in the visible MOKE. changes i n longitudinal and net transverse moments are resolved by measuring both Ke rr rotation and intensity loops, respectively, near the Fe 2p core resonanc e. These X-ray MOKE signals measured using linear incident polarization are more directly interpreted in terms of longitudinal and transverse moments than are the same signals measured using elliptical polarization. Varying p hoton energy near the Fe L-3 line is shown to be an effective means of reso lving distinctly different reversal behavior at the top and bottom of the 2 0 nm thick Fe layer resulting from the strong exchange coupling at the Sm-C o/Fe interface. Measured X-ray MOKE spectra and signals are in qualitative agreement with those calculated using standard magneto-optical formalisms i ncorporating interference between different layers and measured helicity-de pendent magneto-optical constants for Fe. (C) 2001 Elsevier Science B.V. Al l rights reserved.