Electric Field-Induced Modification of Magnetism in Thin-Film Ferromagnets
Martin Weisheit,1,2*
Sebastian Fähler,1,2
Alain Marty,3
Yves Souche,1
Christiane Poinsignon,4
Dominique Givord1
A large electric field at the surface of a ferromagnetic metal
is expected to appreciably change its electron density. In particular,
the metal's intrinsic magnetic properties, which are commonly
regarded as fixed material constants, will be affected. This
requires, however, that the surface has a strong influence on
the material's properties, as is the case with ultrathin films.
We demonstrated that the magnetocrystalline anisotropy of ordered
iron-platinum (FePt) and iron-palladium (FePd) intermetallic
compounds can be reversibly modified by an applied electric
field when immersed in an electrolyte. A voltage change of –0.6
volts on 2-nanometer-thick films altered the coercivity by –4.5
and +1% in FePt and FePd, respectively. The modification of
the magnetic parameters was attributed to a change in the number
of unpaired
d electrons in response to the applied electric
field. Our device structure is general and should be applicable
for characterization of other thin-film magnetic systems.
2 IFW Dresden, Institute for Metallic Materials, Post Office Box 27 01 16, D-01171 Dresden, Germany.
3 Département de Recherche Fondamentale sur la Matière Condensée, Service de Physique des Matériaux et Microstructures, CEA Grenoble, 17 Avenue des Martyrs, F-38054 Grenoble Cedex 9, France.
4 Laboratoire d'Electrochimie de Physicochimie des Materiaux et des Interfaces, Ecole Nationale Superieure d'Electrochimie et d'Electrometallurgie, 1130 Rue de la Piscine, Boîte Postale 75, F-38402 Saint Martin d'Hères Cedex, France.
* Present address: AMD Saxony LLC and Company KG, Materials Analysis Department, Wilschdorfer Landstrasse 101, D-01109 Dresden, Germany.
To whom correspondence should be addressed. E-mail: martin.weisheit{at}amd.com
