Volume 86, Number 6, June 2009
Article Number 67008
Number of page(s) 5
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
Published online 10 July 2009
EPL, 86 (2009) 67008
DOI: 10.1209/0295-5075/86/67008

Measurement of the vortex core in sub-100 nm Fe dots using polarized neutron scattering

Igor V. Roshchin1, 2, Chang-Peng Li2, Harry Suhl2, Xavier Batlle3, S. Roy2, Sunil K. Sinha2, S. Park4, Roger Pynn4, M. R. Fitzsimmons4, Jose Mejía-López5, Dora Altbir6, A. H. Romero7 and Ivan K. Schuller2

1   Physics Department, Texas A&M University - College Station, TX, 77843-4242, USA
2   Physics Department, University of California-San Diego - La Jolla, CA 92093-0319, USA
3   Departament de Fisica Fonamental, Universitat de Barcelona - 08028 Barcelona, Catalonia, Spain, EU
4   Los Alamos National Laboratory - Los Alamos, NM 87545, USA
5   Facultad de Física, Pontificia Universidad Católica de Chile - Santiago, Chile
6   Departamento de Física, Universidad de Santiago de Chile (USACH) - Santiago, Chile
7   Materials Department, CINVESTAV - Querétaro, Mexico

received 2 December 2008; accepted in final form 2 June 2009; published June 2009
published online 10 July 2009

We use polarized neutron scattering to obtain quantitative information about the magnetic state of sub-100 nm circular magnetic dots. Evidence for the transition from a single domain to a vortex state, as a function of the dot diameter and magnetic field, is found from magnetization curves and confirmed by micromagnetic and Monte-Carlo simulations. For 20 nm-thick Fe dots with diameters close to 60 nm, the vortex is the ground state. The magnetization of the vortex core (140 $\pm$ 50 emu/cm3) and its diameter (19 $\pm$ 4 nm) obtained from polarized neutron scattering are in agreement with simulations.

75.75.+a - Magnetic properties of nanostructures.
75.60.-d - Domain effects, magnetization curves, and hysteresis.
61.05.F- - Neutron diffraction and scattering.

© EPLA 2009