Exchange bias of Co/CoO multilayers deposited on nanosphere array

Abstract

The [Co/CoO] 5 multilayer nanocap arrays are fabricated on the colloidal sphere arrays which are prepared on the Si substrate by the self-assembly technology. Compared to bilayer film, the H EB of multilayer film is larger than that of the bilayer film. The increase of H EB for multilayer should be ascribed to the interface increase between FM and AFM layers. In the multilayer film structure, H EB of the nanocap array is bigger than that of the flat film, which is attributed to the decrease of FM layer thickness, the decrease of grain size, and the increase of structural defects caused by curved substrate. And the typical step is observed in flat, and the step is reduced significantly in the nanocap array due to the enhancement of interfacial coupling between neighbor FM layers. For the [Co/CoO] 5 multilayer nanocap array, H EB increases first, and then decreases when CoO sublayer thickness changes. When CoO sublayer thickness is 15 nm, H EB reaches its maximum. This result may be related to the topography of nanostructure multilayer on curved substrate.

Enhanced exchange bias in IrMn/CoFe deposited on self-organized hexagonally patterned nanodots

“…Among them, pseudo-ordered structures of FM/AF bilayers deposited on pre-patterned substrates have been developed recently. 17,18 Although anodized aluminum oxide (AAO) templates are generally used for the fabrication of various one-dimensional nanomaterials, they have also been utilized to create nanodots 19 or networks 6,20 by depositing materials either into the pores or onto the surface of the AAO templates, respectively. Using AAO templates are a promising and convenient approach to achieve exchange biased nanostructures.…”

Graphene mediated domain formation in exchange coupled graphene/Co3O4(111)/Co(0001) trilayers

“…This is in strong contrast to the case for magnetism of Co 3 O 4 /Co bilayers [16], Co on non-magnetic substrates [17], and Co in proximity to other insulating antiferromagnets such as CoO [18,19]. Remarkably, the magnetic hysteresis of the trilayer graphene/Co 3 O 4 (111)/Co(0001) shows virtually no temperature dependence for temperatures as high as 400 K. This is a temperature well above the blocking and antiferromagnetic ordering temperatures observed in Co 3 O 4 /Co or CoO/Co heterostructures, as well as above the Néel temperature (T N ) of ∼40 K (Co 3 O 4 ) or ∼290 K (CoO) [16,[18][19][20][21][22][23][24][25][26]. Although reduced dimensionality and symmetry breaking leading to magnetic proximity effects through crystal-field splitting at Co(III) sites in, e.g., Co 3 O 4 nanowires can enhance T N to ∼60 K [25], in general only paramagnetic behavior of the oxide phase is observed above T N .…”