In-depth resolution of the magneto-optical Kerr effect in ferromagnetic multilayers

Abstract

How does one determine the magnetization state and hysteresis loop corresponding to one of the ferromagnetic ͑FM͒ layers located at a given depth in a stack of FM/non-FM layers by means of the magneto-optical Kerr effect? For this purpose the representation of the Kerr effect in the complex rotation-ellipticity plane is introduced. A depth sensitivity function controlling the Kerr effect is defined and its dependence on the photon energy and angle of incidence is studied. A general way to determine the in-depth location of the FM layer, from which the Kerr signal originates, is proposed. In the case of a FM bilayer structure, previous proposed solutions are discussed within a unified formalism. For a system with three or more FM layers two approaches are proposed to extract selectively the magneto-optical signals originating at individual FM layers: the parallel Kerr vector and cascade numerical projection methods. These methods are successively checked experimentally on simple multilayer structures. Finally, on the basis of the developed approaches a readout solution for multivalued magneto-optical recording in a four-storage-layer structure is proposed.

Speed and efficiency of femtosecond spin current injection into a nonmagnetic material

“…For this technique, it was widely assumed that the measured signal contains only a weighted average response of the entire material. However, as it was shown by Hamrle et al in 2002, one can overcome this limitation by taking advantage of the complex nature of the Kerr response, which can be represented by the complex Kerr angle = θ + iε [24]. This so-called complex MOKE (C-MOKE) was very recently realized in a time-resolved experiment by Schellekens et al [25].…”

“…A more detailed derivation as well as information about the experimental realization can be found in Refs. [24,25].…”

Exploring laser-induced interlayer spin transfer by an all-optical method

“…By rotating the projection axis such that it is orthogonal to one of the individual Kerr vectors, this Kerr vector can be completely removed from the MO signal. To measure magnetization dynamics with material and/or depth sensitivity a setup is required where the projection axis P can be rotated, which can be accomplished in various ways [23,24]. Here, this is done by adding a quarter wave plate (QWP) to a standard double modulation TR-MOKE setup [25].…”

“…Our technique to measure material-specific magnetization dynamics is based on the method proposed by Hamrle et al [23], which is schematically depicted in Fig. 1.…”

Atomic-scale depth selectivity of soft x-ray resonant Kerr effect

“…[6][7][8][9] In these works, the different magnetic properties of the individual layers have been resolved by visible or soft x-ray magneto-optical Kerr effects. In earlier work, 3 we also attempted to resolve depth-varying magnetic properties of a Co layer by the use of standing waves generated from a well-ordered multilayer on top of which the Co layer is deposited.…”