Program Highlights

Magnetic Domain Walls at the Nanoscale: Rigid or Soft?

J. D. Burton, R. F. Sabirianov, S. S. Jaswal, and E. Y. Tsymbal
Nebraska MRSEC
and
O. N. Mryasov
Seagate Research, Pittsburgh

In magnetism, a domain wall (DW) is a region separating two magnetic domains with different magnetization orientations. Within the DW magnetic moments undergo angular reorientation across a finite distance known as the DW width. In bulk transition metal ferromagnets DWs are wide (~100 nm) on the scale of the lattice spacing. This behavior may however be changed at the nanoscale where extremely narrow DWs with a width of the order of a lattice constant have been predicted and found. So far all existing models for DWs assumed that the DW is rigid, i.e. they neglected any spatial variation of the magnitude of the magnetic moment across the DW. In a recent study [Burton et al., Phys. Rev. Lett. 97, 077204 (2006)] researchers at the University of Nebraska MRSEC in collaboration with a scientist at Seagate Research, Pittsburgh, have predicted that magnetic moments of narrow, constrained DWs may be reduced or softened. This behavior is illustrated in the figure which demonstrates results of ab initio calculations performed for a five lattice-constant wide DW in a Ni nanowire. The arrows show the magnitude and direction of the magnetic moments, indicating that the moments within DWs are significantly reduced compared to the magnetic moments in a uniformly magnetized wire. The results of this work are important for developing adequate micromagnetic descriptions of non-collinear spin structures at the nanoscale and their effect on transport properties of nanoscale magnetic devices.
This research is supported by the National Science Foundation, Division of Materials Research, Materials Research Science and Engineering Program, Grant 0213808.