Long-Range Interaction and Magnetic Anisotropy of [(CoP)hard/(NiP)am/(CoP)am/(NiP)am]n Superlattices

We present a study of [(CoP)soft/(NiP)am/(CoP)hard/(NiP)am]n (n ≤ 20) magnetic superlattices (tCoP = 5 nm, tNiP = 4 nm) synthesized via chemical bath deposition (CBD). Atomic force microscopy reveals that the soft magnetic layer is fine-grained (amorphous), whereas the hard magnetic layer exhibits a polycrystalline hexagonal structure. The results demonstrate a long-range interlayer interaction whose magnitude depends on the number of blocks (n). This interaction manifests as multiple resonance peaks in the magnetic resonance spectra: three peaks were observed for structures with n = 5, 10, and 15, while two peaks were identified for n = 20. Temperature dependencies of the interlayer interaction fields were obtained: the interaction between the nearest magnetically hard and soft layers is negative (HJ1 < 0), while the interaction between the soft layers (HJ2) undergoes a sign reversal from positive to negative with increasing temperature at a threshold temperature depending on n. The oscillations of the magnetization saturation field correlate with the magnetic anisotropy fields.