| dbo:abstract
|
- In physics, magnetic skyrmions (occasionally described as 'vortices,' or 'vortex-like'configurations) are statically stable solitons which have been predicted theoretically and observed experimentally in condensed matter systems. Skyrmions can be formed in magnetic materials in their 'bulk' such as in MnSi, or in magnetic thin films. They can be achiral, or chiral (Fig. 1 a and b are both chiral skyrmions) in nature, and may exist both as dynamic excitations or stable or metastable states. Although the broad lines defining magnetic skyrmions have been established de facto, there exist a variety of interpretations with subtle differences. Most descriptions include the notion of topology – a categorization of shapes and the way in which an object is laid out in space – using a continuous-field approximation as defined in micromagnetics. Descriptions generally specify a non-zero, integer value of the topological index, (not to be confused with the chemistry meaning of 'topological index'). This value is sometimes also referred to as the winding number, the topological charge (although it is unrelated to 'charge' in the electrical sense), the topological quantum number (although it is unrelated to quantum mechanics or quantum mechanical phenomena, notwithstanding the quantization of the index values), or more loosely as the “skyrmion number.” The topological index of the field can be described mathematically as where is the topological index, is the unit vector in the direction of the local magnetization within the magnetic thin, ultra-thin or bulk film, and the integral is taken over a two dimensional space. (A generalization to a three-dimensional space is possible)..Passing to spherical coordinates for the space and for the magnetisation, one can understand the meaning of the skyrmion number. In skyrmion configurations the spatial dependence of the magnetisation can be simplified by setting the perpendicular magnetic variable independent of the in-plane angle and the in-plane magnetic variable independent of the radius.Then the topological skyrmion number reads: where p describes the magnetisation direction in the origin (p=1 (−1) for ) and W is the winding number.Considering the same uniform magnetisation, i.e. the same p value, the winding number allows to define the skyrmion with a positive winding number and the with a negative winding number and thus a topological charge opposite to the one of the skyrmion. What this equation describes physically is a configuration in which the spins in a magnetic film are all aligned orthonormal to the plane of the film, with the exception of those in one, specific region, where the spins progressively turn over to an orientation that is perpendicular to the plane of the film but anti-parallel to those in the rest of the plane. Assuming 2D isotropy, the free energy of such a configuration is minimized by relaxation towards a state exhibiting circular symmetry, resulting in the configuration illustrated schematically (for a two dimensional skyrmion) in figure 1. In one dimension, the distinction between the progression of magnetization in a 'skyrmionic' pair of domain walls, and the progression of magnetization in a topologically trivial pair of magnetic domain walls, is illustrated in figure 2. Considering this one dimensional case is equivalent to considering a horizontal cut across the diameter of a 2-dimensional hedgehog skyrmion (fig. 1(a)) and looking at the progression of the local spin orientations. It is worth observing that there are two different configurations which satisfy the topological index criterion stated above. The distinction between these can be made clear by considering a horizontal cut across both of the skyrmions illustrated in figure 1, and looking at the progression of the local spin orientations. In the case of fig. 1(a) the progression of magnetization across the diameter is cycloidal. This type of skyrmion is known as a hedgehog skyrmion. In the case of fig. 1(b), the progression of magnetization is helical, giving rise to what is often called a vortex skyrmion. (en)
- 物理学において、磁気スキルミオン（じきスキルミオン、英: magnetic skyrmions、単にスキルミオンとも）は、磁性体中の渦状スピン配向を準粒子としてモデル化したものである。イギリス人物理学者トニー・スカームの考案したモデルを援用して理論的に予言されたためこの名がある。その後、実験的な観測例も多数報告されている。磁気スキルミオンの定義の大筋は事実上確立されているが、細部では様々に異なる解釈が存在する。 シリコマンガンのようなバルク磁性体や、磁性薄膜上に生じることが知られている。これらはアキラル（図1a）となることもキラル（図1b）となることもあり、動的励起状態として現われることも、安定もしくは準安定状態として現われることもある。 (ja)
- In fisica, lo skyrmione magnetico (occasionalmente descritto come configurazione 'vortice'[1] o 'simile a un vortice') è una quasiparticella che è stata predetta teoreticamente e osservata sperimentalmente in sistemi di materia condensata. Gli skyrmioni magnetici possono formare i cosiddetti materiali "bulk" come lo MnSi, o sottili pellicole magnetiche. Sono chirali di natura, e possono esistere sia come eccitazioni dinamiche che come stati metastabili. (it)
|
| rdfs:comment
|
- 物理学において、磁気スキルミオン（じきスキルミオン、英: magnetic skyrmions、単にスキルミオンとも）は、磁性体中の渦状スピン配向を準粒子としてモデル化したものである。イギリス人物理学者トニー・スカームの考案したモデルを援用して理論的に予言されたためこの名がある。その後、実験的な観測例も多数報告されている。磁気スキルミオンの定義の大筋は事実上確立されているが、細部では様々に異なる解釈が存在する。 シリコマンガンのようなバルク磁性体や、磁性薄膜上に生じることが知られている。これらはアキラル（図1a）となることもキラル（図1b）となることもあり、動的励起状態として現われることも、安定もしくは準安定状態として現われることもある。 (ja)
- In fisica, lo skyrmione magnetico (occasionalmente descritto come configurazione 'vortice'[1] o 'simile a un vortice') è una quasiparticella che è stata predetta teoreticamente e osservata sperimentalmente in sistemi di materia condensata. Gli skyrmioni magnetici possono formare i cosiddetti materiali "bulk" come lo MnSi, o sottili pellicole magnetiche. Sono chirali di natura, e possono esistere sia come eccitazioni dinamiche che come stati metastabili. (it)
- In physics, magnetic skyrmions (occasionally described as 'vortices,' or 'vortex-like'configurations) are statically stable solitons which have been predicted theoretically and observed experimentally in condensed matter systems. Skyrmions can be formed in magnetic materials in their 'bulk' such as in MnSi, or in magnetic thin films. They can be achiral, or chiral (Fig. 1 a and b are both chiral skyrmions) in nature, and may exist both as dynamic excitations or stable or metastable states. Although the broad lines defining magnetic skyrmions have been established de facto, there exist a variety of interpretations with subtle differences. (en)
|
