Strain-induced modification of magnetic structure

and new magnetic phases in rare-earth epitaxial

films

C DUFOUR¹, K DUMESNIL¹ and PH MANGIN²

¹Laboratoire de Physique des Mat\'eriaux, Universit\'e H. Poincar\'e-Nancy I, BP 239,

54506 Vandoeuvre les Nancy C\'edex, France

²Laboratoire L\'eon Brillouin, CEA Saclay, 91000 Gif sur Yvette C\'edex, France

E-mail: mangin@dsm-mail.saclay.cea.fr; dufour@lpm.u-nancy.fr;

dumesnil@lpm.u-nancy.fr

Abstract. Rare earths exhibit complex magnetic phase diagrams

resulting from the competition between various contributions to the

magnetic energy: exchange, anisotropy and magnetostriction. The

epitaxy of a rare-earth film on a substrate induces (i) a clamping to

the substrate and (ii) pseudomorphic strains. Both these effects are

shown to lead to modifications of the magnetic properties in (0 0

1)Dy, (0 0 1)Tb and (1 1 0)Eu films. In Dy and Tb films, spectacular

variations of the Curie temperature have been evidenced.

Additionally, Tb films exhibit a new large wavelength magnetic

modulation. In Eu films, one of the helical magnetic domains

disappears at low temperature whereas the propagation vectors of the

other helices are tilted. The link between structural and magnetic

properties is underlined via magnetoelastic models. Moreover,

molecular beam epitaxy permits the growth of Sm in a metastable dhcp

phase. The magnetic structure of dhcp Sm has been elucidated for the

first time. In this review, neutron scattering is shown to be a

powerful technique to reveal the magnetic structures of rare-earth

films.

Keywords. Magnetic nanostructures; neutron scattering; Curie temperature.

PACS No. 75.30.-m