Subatomic movements of a domain wall in the Peierls potential

Abstract

The discrete nature of crystal lattices plays a role in virtually every material property. But it is only when the size of entities hosted by a crystal becomes comparable to the lattice period--as occurs for dislocations, vortices in superconductors and domain walls--that this discreteness is manifest explicitly. The associated phenomena are usually described in terms of a background Peierls 'atomic washboard' energy potential, which was first introduced for the case of dislocation motion in the 1940s. This concept has subsequently been invoked in many situations to describe certain features in the bulk behaviour of materials, but has to date eluded direct detection and experimental scrutiny at a microscopic level. Here we report observations of the motion of a single magnetic domain wall at the scale of the individual peaks and troughs of the atomic energy landscape. Our experiments reveal that domain walls can become trapped between crystalline planes, and that they propagate by distinct jumps that match the lattice periodicity. The jumps between valleys are found to involve unusual dynamics that shed light on the microscopic processes underlying domain-wall propagation. Such observations offer a means for probing experimentally the physics of topological defects in discrete lattices--a field rich in phenomena that have been subject to extensive theoretical study.

Deaging and Asymmetric Energy Landscapes in Electrically Biased Ferroelectrics

“…The motion of a domain wall through the lattice can be described by a force profile which represents the distribution and strength of various pinning centers [6]. While the lattice itself contains periodic pinning centers (i.e., the Peierls potential [7][8][9][10]), most ferroelastic domain wall widths span several unit cells and these intrinsic effects are typically negligible [11]. Much stronger pinning centers often exist in ferroelectrics, including defect complexes, dislocations, and grain boundaries.…”

Magnetic Stray Field Detection as Guidance for Electronic Transport Measurements in the B-T Phase Diagram of MnSi

“…Therefore, in addition to the detection of local magnetic entities, as e.g. the motion of domain walls [20,21], numerous potential applications in the field of 'spintronics' and skyrmion physics (e.g. for studying their dynamical transport and magnetic properties) are conceivable.…”

Energy repartition in the nonequilibrium steady state

“…In (YBi) 3 (FeGa) 5 O 12 , this is reflected by domain wall widths of 8-11 lattice constants [54]. The material parameters at low temperatures are [54][55][56] an exchange coupling J = 1.29 K and crystalline magnetic anisotropy D = 0.3 K, and lattice constant a = 1.24 nm. An upper bound for the field gradient generated by a position dependent magnetic anisotropy in a temperature gradient can be obtained assuming its low temperature value on the cold side and a vanishing one at the hot side, or ε = (D/ l)a = 4 × 10 −7 K and ε/J = 3 × 10 −7 .…”

“…On the other hand, strong perpendicular anisotropies can be induced by alloying and doping (but preserving high magnetic quality) [51][52][53]. In (YBi) 3 (FeGa) 5 O 12 , this is reflected by domain wall widths of 8-11 lattice constants [54]. The material parameters at low temperatures are [54][55][56] an exchange coupling J = 1.29 K and crystalline magnetic anisotropy D = 0.3 K, and lattice constant a = 1.24 nm.…”