Surface and Interior Magnetic Domain Structures of $\langle 110 \rangle$ Oriented Tb–Dy–Fe Alloy Rods

We investigated the surface and interior magnetic domains by using magnetic force microscopy for two types of Tb
_0.3
Dy
_0.7
Fe
_1.95
crystal growing along the lang110rang direction: 1) crystals annealed at 673 K for 2 h in higher vacuum (5times10
^-5
Pa) and 2) crystals annealed at 723 K for 2 h in lower vacuum (5times10
^-3
Pa). For the former, we observed fine stripe-like domains at the surface. For the latter, we observed the interior domains of the specimen; these were also stripe-like, but with larger average width than the surface domains. X-ray diffraction patterns indicate the formation of a thin iron layer in the surface of the specimens annealed in the lower vacuum. The iron layer, as a "capping" layer, actually acts as a shielding layer for the stray fields emerging from the interior domains underneath, resulting in the wide interior domains