Dominant Role of the Epitaxial Strain in the Magnetism of Core-ShellCo/AuSelf-Organized Nanodots

Abstract

Self-organized Co nanodots on a Au(111) surface have been surrounded by controlled Au rings that progressively cap the entire dots. The magnetic susceptibility of these dots has been measured in situ as a function of the Au coverage. The blocking temperature increases when the Co bilayer dots are surrounded by the first Au atomic layer and decreases with the subsequent capping. This result cannot be explained by interfacial anisotropy which is generally assumed to be the dominant term in the magnetic anisotropy of nanostructures. Using molecular dynamics simulations, we evidence that the large strain inside the Co clusters is the main driving force for the anisotropy changes during the Au encapsulation.

Direct proof of mesoscopic misfit in nanoscale islands by x-ray absorption spectroscopy

“…INTRODUCTION Nanoscale objects on surfaces are intensely studied in solid state physics due to their interesting physical and chemical properties, which are often considerably modified as compared to the bulk [1][2][3][4][5][6][7][8][9][10] . This is because a considerable fraction of the atoms experience a reduced coordination involving broken bonds and significant structural rearrangement [8][9][10][11][12][13][14][15][16] . Despite the decisive importance of the atomic geometry for the physical properties of a nanostructure, comparatively scarce is its precise knowledge, since generally this geometry does not exhibit a well defined long range order [17][18][19][20] .…”

Effects of interparticle interactions in magneticFe/Si3N4granular systems

“…[1][2][3][4] Intense research on this type of systems is being extraordinary fuelled by the refinement of preparation and synthesis methods and the development of characterization techniques. The observation of new phenomena exhibited by such materials at the nanoscale, such as increasing anisotropy, 5,6 rise up of ferromagnetic ͑FM͒ signal due to the modification of electronic configuration 7,8 or glassy state 9 may arise from finite-size effects, interplay between surface and core atoms or surface spin frustration. In the latter case, spin-glasslike features, attributed to the dominant role of surface spins, have been deduced from a de Almeida-Thouless 10 ͑AT͒ dependence of their magnetothermal behavior.…”

Shell pressure on the core of MnO/Mn3O4core/shell nanoparticles

“…2,3 This includes materials with strain-induced ordered structures, 4 materials with tuned thermodynamic properties, 5,6 and materials with tuned and new optical, [7][8][9][10][11][12][13] electronic, 14 electro-optical, 15 magnetoelectric, 16,17 and magnetic [18][19][20] properties. In the case of magnetic properties, attention focused on coupling magnetic and electric properties by strain-induced multiferroic materials, 16,17 on increasing anisotropy by shell-induced strain, 19 and on controlling the core/shell exchange coupling by strain. 18 In the context of exchange coupling, one of the systems that has received more attention in recent years is MnO/Mn 3 O 4 core/shell NPs, an "inverted" system where the core is antiferromagnetic (AF) and the shell is ferrimagnetic, growing epitaxially on the core.…”