Abstract
Mn1.4PtSn is the first material in which antiskyrmions have been observed in ultra-thin single crystalline specimens. While bulk crystals exhibit fractal patterns of purely ferromagnetic domain ordering at room temperature, ultra-thin Mn1.4PtSn lamellae clearly show antiskyrmion lattices with lattice spacings up to several $\mu$m. In the work presented here, we systematically investigate the thickness region from 400 nm to 10 $\mu$m using 100 $\times$ 100 $\mu$m$^2$ -wide Mn1.4PtSn plates, and identify the critical thickness-to-width aspect ratio $\alpha_0 = 0.044$ for the ferromagnetic fractal domain to the non-collinear texture phase transition. Additionally, we also explore these non-collinear magnetic textures below the critical aspect ratio $\alpha_0$ above and below the spin-reorientation transition temperature $T_{SR}$ while applying variable external magnetic fields. What we find is a strong hysteresis for the occurrence of an antiskyrmion lattice, since the antiskyrmions preferentially nucleate by pinching them off from helical stripes in the transition to the field polarized state.
Highlights
Magnetic materials that exhibit topological spin arrangements are promising candidates for future applications, in particular for spintronics
After describing the necessary experimental details, we first discuss the thickness-dependent characteristic features of the real-space patterns obtained by magnetic force microscopy (MFM) in zero field and above the spin-reorientation transition temperature TSR; here we clearly identify the critical thickness of D0 = 4.4 μm for Mn1.4PtSn plates, indicating the transition from the ferromagnetic domain (FMD) to the noncoplanar texture (NCT) state
The corresponding twodimensional fast Fourier transforms (FFTs) [see Figs. 1(d3) and 1(d4)] display two distinct features: (i) a set of blurred streaks originating from the nested domains and (ii) a series of linearly aligned peaks within each streak that correspond to the higher Fourier components of the nonsinusoidal stripe profile
Summary
Magnetic materials that exhibit topological spin arrangements are promising candidates for future applications, in particular for spintronics. Elliptically distorted skyrmions of both handedness as well as the nontopological bubble lattice were shown to appear when applying the symmetry-breaking in-plane magnetic field in combination with an out-of-plane field [22,23] This makes the tetragonal Heusler compounds a unique class of materials hosting a rich variety of controllable magnetic textures. MFM can be effectuated with high precision under the various temperature and magnetic field conditions but, can be applied to investigate near-surface properties of any sample thickness, from monolayer to bulk systems In this sense, MFM is not restricted to the analysis of ultrathin lamellae, but will provide insight for any of these Mn1.4PtSn plate samples. We briefly substantiate and discuss the impact of temperature, especially when cooling below TSR
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