Insertion layer magnetism detection and analysis using transverse magneto-optical Kerr effect (T-MOKE) ellipsometry

This experimental study demonstrates that with transverse magneto-optical Kerr effect (T-MOKE) ellipsometry, it is possible to determine the magneto-optical and magnetic properties of insertion layers, even if they are superimposed onto much bigger magnetic signals from the surrounding structure. Hereby, it turns out to be especially valuable that with T-MOKE ellipsometry one has full and precise quantitative access to the complex value of the magneto-optical reflection matrix component β, because small magneto-optical insertion layer signals do not necessarily increase the absolute size of β, but can lead to observable phase changes of this complex quantity instead. We demonstrate the ability of T-MOKE ellipsometry to detect such small effects precisely and hereby allow for an accurate determination of the alloy concentration dependent onset of ferromagnetism in ultrathin CoxRu1-x insertion layers, that are embedded into a much thicker ferromagnetic structure. In addition, a detailed and quantitative signal analysis allowed us to demonstrate that all CoRu insertion layers in our samples exhibits a magnetization reversal behavior that is independent from the adjacent Y3Fe5O12 (YIG) layers, clearly indicating that both magnetic entities are either not or only very weakly coupled.