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MA: Fachverband Magnetismus

MA 9: Anisotropy/Magnetoelasticity

MA 9.4: Talk

Monday, March 26, 2007, 18:00–18:15, H22

Nonlinear magnetoelastic coupling coefficients in strained Fe, Co and Ni monolayers — •Zhen Tian, Dirk Sander, and Jürgen Kirschner — Max-Planck-Institut für Mikrostrukturphysik,

Magnetoelastic (ME) coupling in magnetic thin films has an essential influence on the magnetic anisotropy. The experimental results[1] in recent years indicate a second-order ME coupling effect in thin films with large epitaxial strain. It is the goal of this study to extend the experiments to compressive strain. We deposited Fe, Co and Ni films on Ir(100) in the thickness range 0.1 to 10 nm. Film stress and ME stress were measured by the optical beam bending method[1]. The magnetic films show large film stress of the order GPa due to the mismatch between the film and the substrate, and we deduce a large epitaxial strain of the order percent in the films. We investigate the correlation between film stress, strain and the ME coupling. Our results indicate that ME coupling coefficients B₁ of Fe films and B₂ of Co and Ni deviate from the bulk value and depend on the film strain є. The experimental results can be fitted with an effective strain-dependent ME coupling coefficient B_i^eff with B_i^eff=B_i+D^effє. Our analysis shows that the nonlinear coefficient D^eff is much larger than the first order coupling term B_i. For Co we obtain B₂ = 5.8MJ/m³ and D^eff=275 MJ/m³ , while the bulk value is 7.7MJ/m³. Our results are discussed in view of recent theoretical predictions[2].

[1] D. Sander: Rep. Prog. Phys. 62, 809(1999).

[2] M. Fähnle, M. Komelj: Phys. Rev. B, 65, 212410 (2002); M. Fähnle, M. Komelj: Phys. Rev. B, 73, 012404 (2006).