NONLINEAR-OPTICAL INVESTIGATIONS OF MAGNETIC HETEROSTRUCTURES

We report second-harmonic magneto-optic Kerr effect investigations of magnetic heterostructures. The heterostructures studied are multilayer s of Si/Al2O3/Cu(50 nm)/Ni81Fe19(x), Si/Al2O3/Cu(50 nm)/Co(2 nm)/Ni81F e19(x), and Si/Al2O3Cu(50 nm)/Ni81Fe19(x)/Cu(5 nm), where x ranges fro m 1 to 30 nm. For films thinner than the optical penetration depth, th e transverse second-harmonic Kerr effect experimentally separates and distinctly identifies each of these multilayered structures. We find t hat the addition of the 2 nm Co layer between Cu and Ni81Fe19 increase s the magnetic signature in the second-harmonic intensity by more than a factor of two. This increase correlates with the observed magnetore sistance increase in spin valves with the addition of Co. For films th icker than the penetration depth, the structures with air-exposed Ni81 Fe19 are identical, but they differ significantly from Ni81Fe19 films capped with Cu. We used spectroscopic ellipsometry to determine the li near optical properties of each film in the structure. Modeling of bot h Cu(50 nm)/Ni81Fe19 and Cu(50 nm)/Ni81Fe19(x)/Cu(5 nm) suggests that the buried magnetic interfaces are better generators of second-harmoni c than the air-exposed Ni81Fe19 surface. There is a distinct decay in the magnetic component of the second-harmonic intensity for film thick nesses below 2 nm. (C) 1997 American Institute of Physics.