Evaluation Of The Exchange Coupling Between Adjacent Magnetic Layers Using Time-Resolved Magneto-Optic Kerr Effect (Trmoke)

Vertical exchange coupling between the adjacent layers of a magnetic multilayer has a strong impact on the magnetization reversal mechanism. Time-resolved magneto-optic Kerr effect (TRMOKE) is used to evaluate the vertical exchange coupling energy per unit film surface J(V) between two Co1-XPtX layers denominated A (x = 27 at. %) and B (x = 22 at. %), separated by a CoCrRu weakly-magnetic layer denominated exchange control layer (ECL), as a function of the ECL thickness d(ECL) in the range of 0-5 nm. The A and B layers have perpendicular anisotropy and thicknesses d(A) = 7 nm and d(B) = 5.6 nm. For this purpose, the dependence of the acoustic magnetization oscillation frequency f(AC) on d(ECL) is measured using TRMOKE and the dependence f(AC)(J(V)) is theoretically assessed using two models: (a) the two-spins model (TSM) assumes a parallel orientation of spins across the thickness of each layer; (b) the chain-of-spins model (CSM) takes into account the possibility of a non-collinear orientation of spins across the thickness of the A and B layers. In the case of d(ECL) greater than or similar to 1 nm corresponding to J(V) less than or similar to 1 erg cm(-2), TSM and CSM offer similar J(V) values. Below d(ECL) (sic) 1 nm, CSM provides a more accurate estimate of J(V) than TSM which underestimates J(V) the more significantly the lower is d(ECL).