Origin of the interlayer exchange coupling in[Co∕Pt]∕NiO∕[Co∕

A. Baruth

¹

,

D.J. Keavney

²

,

John Burton

³

et al.

Abstract

The origin of the oscillatory interlayer exchange coupling in ͓Co/ Pt͔ / NiO / ͓Co/ Pt͔ multilayers is investigated using advanced microscopy and spectroscopy techniques and micromagnetic modeling. X-ray magnetic circular dichroism ͑XMCD͒ measurements show the presence of the canting of Ni spins in the NiO film being greater for antiferromagnetically coupled multilayers than for ferromagnetically coupled ones. This behavior is consistent with the model, which assumes a different sign of the exchange coupling at the two interfaces and the antiferromagnetic layer-by-layer coupling in the NiO film. An unexpectedly short attenuation length of 4 Å for secondary electrons in NiO is measured, which has implications for the interpretation of XMCD data. Domain images obtained using XMCD-photoemission electron microscopy at the Co and Ni resonances indicate that the canting of the Ni spins occurs on both a microscopic and macroscopic scale. The average size of the domains is shown to increase with exchange coupling strength. In antiferromagnetically coupled samples, the competition between magnetostatic and interlayer exchange effects gives rise to a region of overlapping domains. The size of this region scales inversely with coupling strength. Finally, the temperature dependence of the interlayer coupling shows both reversible and irreversible effects. The irreversible effects stem from oxidation/reduction reactions at the Co/ NiO interface. The reversible effects stem from the temperature dependences of the many factors that play a role in the interlayer coupling and exhibit nonmonotonic temperature dependence.

Domain overlap in antiferromagnetically coupled [Co∕Pt]∕NiO∕[Co∕Pt] multilayers

“…It has previously been shown that these multilayers exhibit oscillatory interlayer exchange coupling 3 ͑IEC͒ which occurs domain by domain 10 and is mediated by the canting of Ni spins in the NiO layer. 11,12 For antiferromagnetically ͑AFM͒ coupled samples it was found that there is a relative shift between the domains of the two magnetic layers originating from a competition between the magnetostatic interaction and the AFM IEC. 12 A similar behavior was also observed in ͓Co/ Pt͔ multilayers separated either by Pt 4 or by Ru 5 layers.…”

“…11,12 For antiferromagnetically ͑AFM͒ coupled samples it was found that there is a relative shift between the domains of the two magnetic layers originating from a competition between the magnetostatic interaction and the AFM IEC. 12 A similar behavior was also observed in ͓Co/ Pt͔ multilayers separated either by Pt 4 or by Ru 5 layers. Here using high resolution magnetic force microscopy ͑MFM͒, we perform a detailed study of the domain overlap in ͓Co/ Pt͔ / NiO / ͓Co/ Pt͔ multilayers with various strengths of the IEC.…”

Simultaneous in-plane and out-of-plane exchange bias using a single antiferromagnetic layer resolved by x-ray magnetic circular dichroism

“…12,13 To date, although IP FM/AFM/FM systems have been widely investigated, [9][10][11]14 only a few studies have been performed on FM/AFM/FM coupling in OP systems. 15,16 The increase of perpendicularly magnetized elements in magnetic memories and tunnel junctions, 2,3 as well as the emergence of hybrid IP/OP devices [16][17][18] has recently exposed the need for simultaneously IP and OP exchange biased layers in a single structure.…”

Perpendicular magnetization in CoO (111) layers induced by exchange interaction with ferromagnetic Co and Ni60Cu40 nanoclusters

“…In the opposite, the spins canting in the AFM layers has already been proven experimentally (by neutron scattering) and is supported by micromagnetic calculations. 16 In this present work, this adding contribution to the OOP magnetization can only come from the CoO layer. It is worth to note here that no net magnetization has been observed for the sole CoO layer.…”