Magnetic thin films with perpendicular magnetic anisotropy (PMA) have special attributes for explorations and perpendicular magnetic recording. We have observed three hitherto unknown new features in materials with PMA:
1. Asymmetrical domain nucleation centers that produce domains for only one magnetization direction (Fig. 1).
2. The backward domain wall motion of the asymmetrical nucleation centers is much faster than that of the forward motion.
3. Magnetic domains with a fixed boundary but fading contrast.
These results have been accounted for by a theory that we have developed.
Fig. 1: Evolution of magnetic domain under a perpendicular magnetic field of -17.3 mT (a, b) and +17.3 mT (d, e) and after the field cycling (c, f).
Arrows indicate the asymmetrical centers.
This Work (Scientific and Technological Interests)
We have observed three hitherto unknown new features in materials with PMA:
1. Asymmetrical domain nucleation centers that produce domains
for only one magnetization direction (Fig. 1).
2. The backward domain wall motion of the asymmetrical nucleation
centers is much faster than that of the forward motion.(Fig. 2)
3. Magnetic domains with a fixed boundary but fading contrast.
These results have been accounted for by a theory that we have developed.
Fig. 2: Forward and backward domain wall displacement
for (a)symmetric and (b) asymmetric centers.
Y. L. Iunin, Y. P. Kabanov, V. I. Nikitenko, X. M. Cheng, D. Clarke, O. A. Tretiakov, O. Tchernyshyov, A. J. Shapiro, R. D. Shull,
and C. L. Chien, "Asymmetric domain nucleation and unusual magnetization reversal in ultrathin Co films with
perpendicular anisotropy," Phys. Rev. Lett., 98, 117204 (2007).
D. Clarke, O. A. Tretiakov, and O. Tchernyshyov, "Stripes in thin ferromagnetic films with out-of-plane anisotropy,"
Phys. Rev. B 75, (2007 in press).
