Eur. Phys. J. B 31, 69-74 (2003)
https://doi.org/10.1140/epjb/e2003-00010-2

Exchange coupling in ultrathin epitaxial yttrium iron garnet films

¹ LMOV, UVSQ-CNRS, bâtiment Fermat, 45 avenue des États-Unis, 78035 Versailles Cedex, France
² Institute of Magnetism NASU, 36 Vernadsky Blvd., Kyiv, 03142, Ukraine
³ LPSC, CNRS, 1 place Aristide Briand, 92195 Meudon Cedex, France
⁴ Département de Physique, UVSQ, bâtiment E, 45 avenue des États-Unis, 78035 Versailles Cedex, France
⁵ LMDH, Université Pierre et Marie Curie, Boite 86, 4, place Jussieu, 75252 Paris Cedex 05, France

Corresponding author: ^a popova@lpm.u-nancy.fr

Received: 3 June 2002
Revised: 7 October 2002
Published online: 27 January 2003

Abstract

Magnetic exchange coupling has been observed for ultrathin films of yttrium iron garnet (Y₃Fe₅O₁₂ or YIG). Single-crystalline YIG films were prepared on yttrium aluminium garnet (Y₃Al₅O₁₂ or YAG) substrates by pulsed laser deposition. (111) and (110) oriented substrates were used. Film thicknesses were varied from 180 Å to 4600 Å. Epitaxial growth of YIG on YAG was obtained in spite of the lattice mismatch of 3%. Magnetic hysteresis loops recorded for ultrathin YIG films have a “bee-waist” shape and show a coupling between two different magnetic phases. The first phase is magnetically soft YIG. A composition study by secondary ion mass spectroscopy shows the second phase to be Y₃FeAl_xO₁₂ due to the interdiffusion of Fe and Al at the film/substrate interface. This compound is known to be magnetically harder and to have weaker magnetization than YIG. The coupling of the two phases leads to a hysteresis loop displacement at low temperatures. This displacement varies differently with film thickness for two substrate orientations. Assuming an interfacial coupling, the maximal interaction energy is estimated to be about 0.17 erg/cm² at 5 K for (111) oriented sample.