Influence of Superparamagnetism on Exchange Anisotropy at CoO/[Co/Pd] Interfaces

Abstract

Magnetic systems exhibiting an exchange bias effect are being considered as materials for applications in data storage devices, sensors, and biomedicine. Because the size of new magnetic devices is being continuously reduced, the influence of thermally induced instabilities in magnetic order has to be taken into account during their fabrication process. In this study, we show the influence of superparamagnetism on the magnetic properties of an exchange-biased [CoO/Co/Pd] multilayer. We find that the process of progressive thermal blocking of the superparamagnetic clusters causes an unusually fast rise of the exchange anisotropy field and coercivity and promotes easy-axis switching to the out-of-plane direction.

Magnetization Reversal Mechanism in Exchange-Biased Spring-like Thin-Film Composite

“…The shape of the ZFC and FC curves is typical for ferromagnets and indicates that the composite reveals ferromagnetic behavior in the whole temperature range from 10 to 300 K. Since both curves are monotonic without any maxima, no superparamagnetic or superferromagnetic effects have to be taken into account during further analysis of the magnetization switching process. 24 Additionally, in both FC and ZFC curves, there is a small increase of the signal at low temperatures. Such behavior suggests that a small paramagnetic contribution is present in the system.…”

“…[21,22] As an antiferromagnetic material for the exchange bias effect studies we have chosen cobalt oxide CoO since its properties are well known and the Co/CoO interface is considered to be a model system for such investigations. [23][24][25][26] Here, we present studies on the cooling field influence on the magnetization reversal mechanism for the exchangebiased system where the CoO antiferromagnetic layer is sandwiched between two [Co/Pd] ferromagnetic multilayers with different coercivities. The issue of the cooling field impact on the magnitude and sign of the exchange bias field has been recently raised in a few research papers.…”

Magnetic reversal in perpendicularly magnetized antidot arrays with intrinsic and extrinsic defects

“…It was assumed that 10% of randomly selected grains is defected with the zero anisotropy constant K U . The presence of such grains could be caused by the lattice misalignment, high local roughness of Co/Pd interfaces, or the lack of continuity of the constituent layers, which is typical for thin multilayers deposited non-epitaxially on the rough substrates 47,48 . We assigned nominal value of the uniaxial anisotropy constant to the remaining 90% of the grains with a unique direction of K U axis for each grain, which is expected for multilayers with distorted interfaces caused by heterogeneous growth.…”

Room Temperature Magnetic Memory Effect in Cluster-Glassy Fe-Doped NiO Nanoparticles

“…At 500 Oe, a plateau is observed below 100 K from the FC curve of 0.5%, and 1% samples. Such FC curve shape in the low-temperature region is usually observed for super-spin-glasses (SSG) and super-ferromagnetic (SFM) materials, suggesting collective spin behavior [ 44 ]. At a finite interparticle distance in the magnetic system, more complex systems can be encountered due to magnetic interactions, especially of dipolar origin.…”