The role of proximity induced magnetization in interlayer coupling in ferromagnetic/heavy metal/ferromagnetic multilayers

Interlayer exchange coupling between ferromagnetic thin films through non-magnetic spacers is central to spintronics. While coupling via chromium and ruthenium is explained by the Ruderman-Kittel-Kasuya-Yosida interaction, coupling through heavy metals such as platinum remains less clear. One proposed mechanism involves proximity-induced magnetization in platinum, arising from electronic hybridization with adjacent ferromagnets. We present experimental evidence connecting this proximity effect with interlayer coupling in cobalt iron/platinum/cobalt iron structures as a function of platinum thickness. Magnetic hysteresis loops from magneto-optical Kerr effect and resonant magnetic X-ray measurements reveal a transition from two-step to single-step magnetization reversal as Pt thickness decreases, marking the onset and strengthening of coupling. Resonant magnetic X-ray reflectivity provides depth profiles of the induced platinum magnetization that become continuous through the platinum for the thinner platinum interlayers. These findings provide insight into a mechanism for interlayer coupling in multilayer systems containing heavy metals.