Ha Wierenga

Interface magnetism studied by optical second harmonic generation

Optical second harmonic generation studies of Co/Au interfaces show a clear magnetic field induced effect at these interfaces, leading the way to a nonlinear optical probe that is uniquely sensitive to surface and interface magnetism.

Magnetization-induced optical second-harmonic generation from magnetic multilayers

Abstract The optical second-harmonic intensity generated by magnetic multilayers appears to depend strongly on the magnetization. Combining interface and magnetic sensitivity, magnetization-induced optical second-harmonic generation provides a unique tool to study magnetic interface properties. The underlying theoretical analysis is given and illustrated with an example and experiments on Co/Au multilayers.

Direct Comparison of Nonlinear and Linear Kerr-Effect Measurements on Thin Co Films on Cu(001)

It is shown that magnetization-induced second harmonic generation (SHG) is a powerful tool for investigating surfaces and buried interfaces. The source of the SHG is bound to the interface within a region of less than 2 monolayers. Changes in the electronic structure of the Co and especially the Cu-covered Co films as a function of the Co/Cu film thickness are observed.

SEPARATION OF INTERFACE AND BULK CONTRIBUTIONS IN 2ND-HARMONIC GENERATION FROM MAGNETIC AND NONMAGNETIC MULTILAYERS

We discuss the separation problem of bulk vs interface contributions in optical Second-Harmonic Generation (SHG). A new method is presented, which — in special cases — provides a full separation of all interface and bulk tensor components. The method is based on measurements in a thin-film geometry, and the relation between two bulk tensor components obtained from group-theoretical arguments. The separation problem in its strict sense is shown to be absent in Magnetization-induced SHG (MSHG). Though, in practice, also in the MSHG case interface and bulk contributions can be closely resemblant. The approach is illustrated by second-harmonic experiments on C60 thin films. SHG in this system is found to be completely dominated by bulk processes.

Nonlinear and linear Kerr studies of Co/Cu multilayers

Magnetization induced optical second harmonic generation (MSHG) in combination with the magneto-optical Kerr effect (MOKE) was used to study thin Co films and Cu/Co multilayers of thicknesses between 1 and 20 monolayers (ML) grown on a Cu(001) substrate. From the different dependence of MSHG and MOKE on Co film thickness we get direct information about the interface sensitivity of MSHG. Modifying the vacuum/Co interface by gas adsorption yields the relative contributions of the vacuum/Co and the Co/Cu(001)-substrate interfaces. Both MSHG and MOKE data can be accurately described by a multiple reflection model.