28 research outputs found
Magnetic reconfiguration of MnAs/GaAs(001) observed by Magnetic Force Microscopy and Resonant Soft X-ray Scattering
We investigated the thermal evolution of the magnetic properties of MnAs
epitaxial films grown on GaAs(001) during the coexistence of
hexagonal/orthorhombic phases using polarized resonant (magnetic) soft X-ray
scattering and magnetic force microscopy. The results of the diffuse satellite
X-ray peaks were compared to those obtained by magnetic force microscopy and
suggest a reorientation of ferromagnetic terraces as temperature rises. By
measuring hysteresis loops at these peaks we show that this reorientation is
common to all ferromagnetic terraces. The reorientation is explained by a
simple model based on the shape anisotropy energy. Demagnetizing factors were
calculated for different configurations suggested by the magnetic images. We
noted that the magnetic moments flip from an in-plane mono-domain orientation
at lower temperatures to a three-domain out-of-plane configuration at higher
temperatures. The transition was observed when the ferromagnetic stripe width L
is equal to 2.9 times the film thickness d. This is in good agreement with the
expected theoretical value of L = 2.6d.Comment: 16 pages in PD
Domain wall formation and spin reorientation in finite-size magnetic systems
We investigate the formation of stable one-dimensional N\'eel walls in a
ferromagnetic slab with finite thickness and finite width. Taking into account
the dipolar, the exchange and the uniaxial anisotropic crystalline field
interactions, we derive an approximative analytical self-consistent expression
that gives the wall width in terms of ratios between the three different energy
scales of the problem. We also show that, even when the crystalline anisotropy
does not favour the formation of domain walls, they can yet be formed due to
the dipolar interaction and the finiteness of the system. Moreover, using a
Stoner-Wohlfarth approach, we study the magnetization reorientation inside the
domains under the action of an external magnetic field and obtain the
respective hysteresis loops, showing that their shapes change from squared to
inclined as the width of the slab varies. Finally, we discuss possible
applications of this model to describe qualitatively some recent experimental
data on thin films of MnAs grown over GaAs substrates.Comment: 11 pages, 10 eps figure