In nanoscale magnetic multilayers, capping layers are often used to protect the underlying magnetic layers from oxidation. However, little research has investigated possible long-range coupling interactions between nonmagnetic transition metal (TM) capping layers and neighboring magnetic layers. In this paper, the temperature (T) dependence of the magnetic moment of different thicknesses of cobalt (Co) was studied in a tantalum (Ta)/Co/TM trilayer structure with four TM capping layers, where the TMs were Ta, Chromium (Cr), titanium (Ti), and zirconium (Zr), respectively. It was found that the capping layer had a large effect on the phase-transition behavior and thermal stability of the Co layer. In the Ta and Cr layers, the T-dependence of Co magnetic moment showed nonmonotonic behavior, and in the Ti and Zr layers, the Co M-T curve exhibited very few effects of the capping layer. We attribute this phenomenon to the long-range coupling between the Co and TM layers. Furthermore, the coupling mechanism was linked to the indirect magnetic exchange coupling in Co/TM multilayers, similar to the Ruderman-Kittel-Kasuya-Yoshida coupling. The results of this work will support further development of the understanding of the coupling between the 3d ferromagnetic (FM) metal and nonmagnetic TM at nanoscales. Relative to potential applications, it will inspire us to rediscover the role of both the TM capping layer and buffer nonmagnetic layer in FM/TM multilayers, especially for nanoscale magnetic multilayers with spin-dependent effects, such as spin valves, spin halls, spin transfer torque, and spin–orbit coupling, which are in widespread use in the manufacture of various spintronics devices.

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A negative magnetoresistance (MR) was observed at room temperature in a Co/Py transverse “coercivity heterostructures” configuration thin film, and it can be explained by domain wall scattering at the boundaries of the Co and Py. We point out that the novel “soft” and “hard” transverse “coercivity heterostructures” not only can be used to study domain wall resistance of variety magnetic materials, but also have potential application in fabricating domain wall devices.

We focus on the anomalous Hall effects (AHEs) of Co/Ni multilayers with perpendicular magnetic anisotropy (PMA) by using Ta, Nb, and Cu as the buffer and top layer. An un-conventional AHE behavior was found in which the AH resistance exhibits two anti-symmetric peaks in the presence of a magnetic field. Moreover, Co/Ni multilayers with a Ta neighboring layer show reverse AH resistance compared to the Nb and Cu neighboring layers, except Ta bottom and Cu capping layers. The former can be explained by considering the influence of the external magnetic field on the interfacial spin orbit interaction due to spontaneous symmetry breaking at the ferromagnetic (FM)/FM layer interface. Furthermore, the reverse Co/Ni AHE with a Ta adjacent layer can be interpreted as the leakage spin current of proximity effects from Ta due to its larger spin–orbit coupling, and finally, taking the shunting action of the Cu layer into account, the Co/Ni AHE with Ta and Cu adjacent layers can also be explained. Our results provide a clear physics picture of the AHE in a two-dimensional nano-scaling FM/FM interface with PMA; in particular, this work shows that the non-magnetic adjacent layer with large spin–orbit coupling will play an important role in the understanding of AHE in two-dimensional FM multilayers.