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For almost a century, the width of magnetic domain walls (DW)
has been believed to be determined by material properties only.
However, recent investigations of DWs in nanometer-scale systems
have revealed new physical properties caused by the geometrical
confinement of the magnetization and particularly by the ability
of constraining DWs to very small widths. Both for a basic understanding
and potential applications, it is important to understand quantitatively
how DW properties can be modified by means of geometry.
For instance, we have studied magnetic 180° Néel domain
walls pinned in micron-sized Fe20Ni80 elements containing geometrical
constrictions (Figure 1) by spin
polarized scanning electron microscopy and numerical simulations.
The confinement results in a strong reduction of the width of 180°
Néel walls compared to unconstrained systems. For a 7.5-nm-thick
sample, the wall width in the extended film is measured to be 700
nm. This is reduced to 100 nm in a 10 µm × 4 µm
element with contriction dimensions of 100 nm × 500 nm (Figure
2).
We have furthermore shown how, by controlling the constriction
dimensions, the wall width can be tailored and the type of wall
modified.
References
| [1] |
P.-O. Jubert, R. Allenspach, and
A. Bischof, Phys. Rev. B 69, 220410(R) (2004). |
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