Magnetostatics of room temperature compensated Co/Gd/Co/Gd-based synthetic ferrimagnets

Abstract

Flexibility for interface engineering and access to all-optical switching of the magnetization make synthetic ferrimagnets an interesting candidate for advanced optospintronic devices. Moreover, due to their layered structure and disordered interfaces, they also bear promise for the emerging field of graded magnetic materials. The fastest and most efficient spin–orbit torque driven manipulation of the magnetic order in this material system generally takes place at compensation. Here, we present a systematic experimental and modeling study of the conditions for magnetization compensation and perpendicular magnetic anisotropy in the synthetic ferrimagnetic Co/Gd/Co/Gd system. A model based on partial intermixing at the Co/Gd interfaces of this system has been developed which explains the experiments well and provides a tool to understand its magnetic characteristics. More specifically, this work provides further insight into the decay of the Co proximity-induced magnetization in the Gd, and the role the capping layer plays in the Gd magnetization.

Exploring THz exchange resonances in synthetic ferrimagnets with ultrashort optically induced spin currents

“…1 g. We note that, even though the samples are deposited as multilayers, significant intermixing between Co and Gd is expected at the interface when sputter depositing at room temperature [33][34][35][36]. As the Co thickness is only 0.8 nm, the intermixing depth in thin RE/TM multilayers is expected to be in a similar order of magnitude as the individual layer thickness, leading to significant alloy-like regions [37].…”

“…Thus, it only shows a finite magnetization within the partially intermixed Co/Gd and Gd/Co interfaces as well as proximity-induced magnetization in the regions close to the interfaces. As one moves away, this induced magnetization-and thus the angular momentum-decreases exponentially [37]. Secondly, increasing the Gd thickness decreases the average exchange parameter λ in eq.…”

Exploring terahertz-scale exchange resonances in synthetic ferrimagnets with ultrashort optically induced spin currents

“…We note that, even though the samples are deposited as multilayers, significant intermixing between Co and Gd is expected at the interface when sputter depositing at room temperature [34][35][36][37]. As the Co thickness is only 0.8 nm, the intermixing depth in thin RE/TM multilayers is expected to be on a similar order of magnitude as the individual layer thickness, leading to significant alloy-like regions [38].…”

“…Thus, it only shows a finite magnetization within the partially intermixed Co/Gd and Gd/Co interfaces as well as proximityinduced magnetization in the regions close to the interfaces. As one moves away, this induced magnetization-and thus the angular momentum-decreases exponentially [38]. Second, increasing the Gd thickness decreases the average exchange parameter λ in Eq.…”

Aging and passivation of magnetic properties in Co/Gd bilayers

“…We choose the areanormalized moment, m, as defining the magnetization requires us to define a thickness by which to normalize. However, in that case, coarse assumptions have to be made about the intermixing and magnetization profile in Gd, 33 making area normalization the more consistent choice. The resultant square hysteresis loop in m for OOP SQUID indicates perpendicular magnetic anisotropy, as expected for thin films of Co on Pt.…”