Orange peel coupling in multilayers with perpendicular magnetic anisotropy: Application to (Co/Pt)-based exchange-biased spin-valves

Abstract

Néel's theory of magnetostatic coupling between two magnetic layers with inplane magnetization separated by a non-magnetic spacer has been extended to the case of multilayers with perpendicular anisotropy. It is shown that the presence of a correlated roughness between the successive interfaces induces an interlayer coupling through the spacer analogous to the well-known orange peel coupling. However, depending on the parameters describing the interfacial roughness, the magnetic anisotropy and the exchange stiffness constant, this coupling can favor either parallel or an antiparallel alignment of the magnetization in the two ferromagnetic layers. This model was used to quantitatively interpret the variation of interlayer coupling vs. thickness of Pt spacer layer in out-of-plane magnetized exchange-biased spin-valves comprising (Pt/Co) multilayers as free and pinned layers. It is shown that the net coupling can be interpreted by the coexistence of perpendicular orange peel and oscillatory RKKY couplings. Interestingly, since these two couplings have different thickness dependence, in certain range of Pt thickness, the coupling changes sign during growth, being antiferromagnetic at the early stage of the growth of the top (Co/Pt) multilayer but ferromagnetic once the growth is completed.

Strong interlayer exchange coupling and high post-annealing stability in perpendicularly magnetized [Pt/Co]/Ru/[Co/Pt] structures

“…2 can be explained by the formation of pinhole contacts and reduction of the effective Ru thickness with annealing; both phenomena are strongly related to the inter-diffusion of Ru 8,9,20 and non-uniformities at the interface. 21 The observed J ex,1 value of 2.55 ergs/cm 2 for t Ru = 0.35 nm was higher than the value of 2.2 ergs/cm 2 reported previously for a similar [Pt/Co] based SyF structure. 22 Although the J ex,1 value was reduced to 1.33 ergs/cm 2 after 2016) annealing at 400 o C, this value was still higher than the limiting value of 0.70 ergs/cm 2 required to prevent read/write failures.…”

Phase diagram in exchange-coupled CoTb/[Co/Pt] multilayer-based magnetic tunnel junctions

“…In this last case, the soft electrode reversal magnetization loop is slightly shifted along the negative horizontal field axis, as a result of the ferromagnetic coupling between the electrodes across the MgO tunnel barrier. As reported previously in in-plane [20][21][22] and out-of-plane [23] magnetized MTJs with thick tunnel barriers, this ferromagnetic coupling is attributed to an "orange peel"-type magnetic coupling between both electrodes. This interaction will be particularly important to explain regions of the phase diagram where domain duplication occurs (see Sec.…”

Single shot ultrafast all optical magnetization switching of ferromagnetic Co/Pt multilayers

“…[13][14][15] . An RKKYtype of exchange [13][14][15][16] or a dipolar orange peel coupling 13,17 could explain such AFM coupling.…”