Magnetic and crystalline structure of
FePt nanoparticles
M. Farle
Universität Duisburg-Essen, Fachbereich
Physik, Lotharstr. 1, 47048 Duisburg, Germany
Element-specific magnetism and
interface properties inside a nanoparticle can be studied by combining
superparamagnetic resonance and different x-ray absorption spectroscopies [1]. Different shapes and structures of
nanoparticles are obtained by different organometallic synthesis routes or by
enhancing diffusion processes during the formation of particles in gas-phase
condensation methods [2]. Using the
magnetic alloy FePt as an example the possibilities will be discussed. In
ligand and oxide free FexPt1-x icosahedral particles (6
nm), which have been annealed to 800 K, we find enhanced (330 %) orbital magnetism
at the Fe site [1,2] and a reduced orbital magnetism at the Pt site. Modifications
of the magnon excitation spectrum due to size effects in FePt nanocubes [3]
lead to changes of the temperature dependence of the magnetization and can be
experimentally determined. The
special importance of correlating experimental structural and magnetic findings
with ab-initio calculations will be demonstrated by showing experimentally
resolved surface reconstructions of few percent [4] and theoretical results confirming
that below 3 nm diameter the formation of fct L10 chemically ordered FePt
nanoparticles is energetically not favored [5].
Supported
by National Center of Electron Microscopy, Berkeley, Deutsche Forschungsgemeinschaft
SFB 445, and EU network “Syntorbmag”.
[1] C.
Antoniak et al, Phys. Rev.
Lett. 97 (2006) 117201
[2] O.
Dmitrieva, et al. Phys. Rev. B 76 (2007) 064414
[3] O.
Margeat, et al. Phys. Rev. B 75 (2007) 134410
[4] Rongming Wang, et al, Phys. Rev.
Lett. 100 (2008) 017205
[5] M.
E. Gruner, et al, Phys. Rev. Lett. 100
(2008) 087203
Contact:
Prof. Dr. Michael
Farle
Fachbereich Physik,
Experimentalphysik – AG Farle
Universität
Duisburg-Essen
Lotharstr. 1
47048
Email: farle@uni-due.de
Web: http://agfarle.uni-due.de
Tel./Fax: +49 (0) 203 379-2075
/-2098