Fractional topological charges in two-dimensional magnets

Magnetic skyrmions and antiskyrmions are characterized by an integer topological charge Q = +/- 1, describing the winding of the magnetic orientation. Half-integer winding numbers, Q = f 12, can be obtained for magnetic vortices (merons). Here, we discuss the physics of magnets with fractional topological charge which is neither integer nor half-integer. We argue that in ferromagnetic films with cubic anisotropy, textures with Q = +/- 1/6 or +/- 1/8 arise naturally when three or more magnetic domains meet. We also show that a single magnetic skyrmion with Q = -1 can explode into four fractional defects, each carrying charge Q = - 41. Additionally, we investigate a point defect with a nonquantized fractional charge (Q not equal n/m, n, m is an element of Z) which can move parallel to a magnetic domain wall. Only defects with fractional charge lead to an Aharonov-Bohm effect for magnons. We investigate the resulting forces on a fractional defect due to magnon currents.