The correlation between mechanical stress and magnetic properties of ultrathin films

Abstract

The cantilever bending beam technique was applied to measure film stress, film magnetization and magneto-elastic coupling in nanometre Fe films grown epitaxially on W substrates. A simple optical deflection technique yielded sub-monolayer sensitivity for stress measurements and was used to determine magnetization and magnetostrictive properties of nanometre Fe films in situ. The combination of an electromagnet inside an ultra-high-vacuum chamber with a rotatable external magnet was employed to perform magneto-optical Kerr-effect measurements in the transversal, longitudinal and polar geometry in fields of up to 0.4 T. Examples for stress-driven structural changes in monolayer Fe films are discussed with respect to the unusual high coercivity found for sesquilayer Fe films and the re-orientation of the easy axis of magnetization in Stranski-Krastanov Fe films. The direct correlation between strain and magnetism was exploited to measure the magnetostrictive bending of the film-substrate composite. The magnitude and sign of the magneto-elastic coupling coefficient were found to depend on the film thickness, in contrast to the respective bulk values.

Magnetic imaging with spin-polarized low-energy electron microscopy

“…This SRT is also observed for thinner deposits, when room temperature grown Fe films are subsequently annealed a few minutes at several hundred K [115,116]. However, in that case, the SRT is accompanied with the dewetting of the Fe film and the formation of islands elongated along the [001] direction.…”

“…However, in that case, the SRT is accompanied with the dewetting of the Fe film and the formation of islands elongated along the [001] direction. Different factors have been suggested as the driving mechanism for this SRT: reduction of magnetoelastic anisotropy (stress relief during the annealing procedure), strong shape anisotropy of the elongated islands, or reduction of surface anisotropy (due to the change in the film morphology, islands are much thicker than the nominal thickness of the as-grown Fe film) [115]. In this context, a key question is: what influence has the dewetting dynamics on the SRT?…”

Structure and perpendicular magnetization of Fe/Ni(111) bilayers on W(110)

“…A detailed growth study on Ni/W͑110͒ including STM, LEED, and stress measurements will be published elsewhere. 3 To clarify whether Fe grows in the fcc structure, angleresolved Auger electron spectroscopy ͑ARAES͒ 4 was performed. To a good approximation, high energy Auger electrons are emitted isotropically by any one atom.…”

Core-level spectroscopy of the Ni/W(110) interface: Correlation of W interfacial core-level shifts with first-layer Ni phases

“…In addition to these basic structural and electronic studies of Ni/W(110), the chemical and catalytic properties of this interface have been extensively investigated [4,11,[22][23][24][25][26][27]. There have also been numerous measurements of the magnetic properties of Ni/W(110) thin films [28][29][30][31][32][33], which have been extended to epitaxial Fe films grown on Ni/W(110) [36][37][38][39][40][41]. Femtosecond electron dynamics in Ni/W(110) films have also been investigated [34,35].…”