The effect of the single-spin defect on the stability of the in-plane vortex state in 2D magnetic nanodots

• Published in: Journal of nanoparticle research : an interdisciplinary forum for nanoscale science and technology Vol. 13; no. 11; pp. 6075 - 6083
• Main Authors: Mamica, S., Lévy, J.-C. S., Depondt, Ph, Krawczyk, M.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01-11-2011; Springer Nature B.V; Springer Verlag
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Condensed Matter; Defects; Fluid flow; Inorganic Chemistry; Lasers; Materials Science; Nanocomposites; Nanomaterials; Nanoparticles; Nanostructure; Nanotechnology; Optical Devices; Optics; Photonics; Physical Chemistry; Physics; Special Issue: Nanostructured Materials 2010; Stability; Two dimensional; Vortices; Ground state stability; Magnetic vortices; Magnetic nanodots; Localized spin waves
• ISSN: 1388-0764; 1572-896X
• DOI: 10.1007/s11051-011-0308-0

The aim of this study is to analyse the stability of the single in-plane vortex state in two-dimensional magnetic nanodots with a nonmagnetic impurity (single-spin defect) at the centre. Small square and circular dots including up to a few thousand of spins are studied by means of a microscopic theory with nearest-neighbour exchange interactions and dipolar interactions fully taken into account. We calculate the spin-wave frequencies versus the dipolar-to-exchange interaction ratio
d
to find the values of
d
for which the assumed state is stable. Transitions to other states and their dependence on
d
and the vortex size are investigated as well, with two types of transition found: vortex core formation for small
d
values (strong exchange interactions), and in-plane reorientation of spins for large
d
values (strong dipolar interactions). Various types of localized spin waves responsible for these transitions are identified.