Coupling of Ni and NiFe films through an intervening nonmagnetic film

The magnetic coupling of 20‐nm‐thick Ni and Ni78Fe22 films through intervening Ag film has been investigated by ferromagnetic resonance (FMR) at 33 GHz. Films were deposited by e‐beam evaporation on glass in the order glass/Ag/Ni/Ag/NiFe/Ag. The Ag over‐ and underlays were 20 nm thick; the central Ag‐film thickness was varied between 0 and 20 nm. The coupling of the two ferromagnetic films, A and B, through the interface is modeled by adding −KMA⋅MB to the free energy per unit area. The FMR‐mode positions are found from the solutions of a quadratic in K. Subsequently, FMR‐mode intensities and linewidths are computed. Input data for these calculations were obtained from observations made on uncoupled Ni and NiFe films. From in‐plane dc‐field date a variation of K was deduced with a coupling film thickness t of the form exp(−t/τ) with τ equal to 2.68 nm. Limited FMR data taken with the dc field normal to the specimen are consistent with a weak coupling, K∼t−0.83. Little coupling was found in a glass/SiO2/Ni...