Switching-mode-dependent magnetic interlayer coupling strength in spin valves and magnetic tunnel junctions

Abstract

We have studied the magnetization reversal dynamics of spin valves and magnetic tunnel junctions deposited on step bunched silicon substrates with a strong topological modulation. Our measurements show that the magnetization reversal is dominated by domain wall propagation at low field sweep rates and nucleation processes at high sweep rates. The magnetostatic orange peel coupling present in quasi-static conditions between the magnetic layers disappears when switching by nucleation becomes dominant. Micromagnetic simulations show that this phenomenon can be explained taking into account the modulated topology of the substrate

Influence of topography and Co domain walls on the magnetization reversal of the FeNi layer inFeNi∕Al2O3∕CoRomanens1, Vogel2, Kuch3 et al. 2006Phys. Rev. BSelf Cite8081View full textAdd to dashboardCite

“…In fast dynamic measurements, coercivities increase and the field range over which the magnetization reverses (magnetization transition) is broader than in quasi-static conditions. 6 A large difference in quasistatic coercivity between the two magnetic layers is therefore needed in order to allow the FeNi magnetization to be switched without changing the Co magnetization in our fast dynamic measurements.…”

“…Steps with an orientation perpendicular to the easy magnetization axis are at the origin of a strongly localized orange-peel coupling. 6 On the other hand, steps parallel to the easy magnetization axis induce strong demagnetizing effects when domain walls are located on these steps. This causes a pinning of the domain walls that hinders reversal by domain wall propagation.…”

“…The roughness also influences the domain wall pinning and therefore the magnetization reversal. In a previous paper, 6 we have revealed the effect of modulated roughness, induced by deposition on step-bunched Si substrates, on the magnetization reversal and coupling in magnetic trilayers. Steps with an orientation perpendicular to the easy magnetization axis are at the origin of a strongly localized orange-peel coupling.…”

Magnetization reversal signatures in the magnetoresistance of magnetic multilayers

“…direction, i.e., α H = 0 • , present two distinctive hysteresis loops, which can be assigned to the intrinsic magnetization reversal behavior of the two FM layers. The free-FM layer exhibits an individual hysteresis loop with a residual shift from the zero field (∼−1.2 mT), which might originate from a magnetostatic "orange-peel" coupling with the pinned-FM layer, 14 and low coercivity (∼ 0.9 mT). The pinned-FM layer presents another individual hysteresis loop shifted away from the zero magnetic field (μ 0 H E ≈ −7 mT) due to the unidirectional exchange anisotropy with the adjacent AFM layer 15 and larger coercivity (3 mT).…”

Magnetization dynamics in microscopic spin-valve elements: Shortcomings of the macrospin picture

“…This finding is surprising, considering the fact that the dynamical behavior of the local magnetization driven by the local effective field H ef f could influence the response of a spin-valve sensor and the damping coefficient. Besides the shape-induced demagnetization field, H ef f contains contributions from the correlated roughness at the FM/NM interfaces 16 and stray fields from inhomogeneously magnetized regions in one of the layers. [17][18][19] An inhomogeneous interlayer thickness may cause a laterally varying indirect coupling field.…”