Magnetic Domain Structures in Thin Uniaxial Plates with Perpendicular Easy Axis

Abstract

We present a convenient formulation of the single-domain energy in the wall-energy model and minimize the total energy of a lattice of cylindrical domains and of a parallel-stripe array in an infinite plate. The latter structure is shown to have the lower energy for external transverse fields Hex<H1 while the lattice is favored for H1≤Hex<H2. The critical domain sizes and fields bounding these structures are calculated as functions of the plate thickness and the material parameters. The factors which affect the evolution of the domain structures in finite and nearly defect-free plates are discussed and the following conclusions drawn: Domain nucleation is favored by the presence of nonuniformities such as cracks or mounds. Stripes nucleated at cracks or boundaries expand and contract with one end tied to the nucleation point and there may be only as many stripes as nucleation centers. An energy barrier inhibits the separation of a domain from (or the joining to) a free edge boundary or another domain. Closed domains are repelled by boundaries and alternate between stripe- and bubble-domain configurations as the local field varies below and above the critical stripe-bubble instability value. The qualitative conclusions can be quantified to some extent in the wall-energy model and provide a satisfactory explanation of the domain structures observed in a high-mobility garnet film.

Magnetic anisotropy in epitaxial Mn5Ge3films

“…The comparison between the shape of the magnetization curves for the two systems is striking and suggests the presence of a stripe domain structure in Mn 5 Ge 3 films at least thicker than 25 nm. The singularity in the magnetization curves in the perpendicular configuration can indeed be attributed to sudden nucleation of magnetic domains with opposite magnetization 29,30 while the remanence in the in-plane magnetization curves originates from the magnetization reversal at the center of the wall. In the Mn 5 Ge 3 system, the magnetization reorientation from fully in plane to fully out of plane occurs therefore between 10 and 25 nm; as a matter of fact, the 16-nm-thick film depicts an intermediate regime with a slight opening of the M-H curve over a range of fields comprised between the two saturation fields.…”

Modified current-induced domain-wall motion in GaMnAs nanowires

“…σ DW can be deduced from the spontaneous demagnetized state, which could be observed in the nucleation pad at 104 K (figure 4). However, the observed state is far from the ideal demagnetized structure consisting of perfect stripe domains [24][25][26] , and the relevant stripe periodicity for comparison with the usual formula is not obvious. From figure 4, we have assumed that the periodicity lies between the smallest and the largest width of the observed ribbons, which are 2 µm and 6 µm respectively.…”

Synthesizing skyrmion bound pairs in Fe-Gd thin films

“…24,25 The new development presented here is the topological aspect. While many bubble materials show bubbles of zero winding number, they can also develop skyrmions with nontrivial winding numbers.…”