Skyrmion lattice in the doped semiconductor ${\text{Fe}}_{1-x}{\text{Co}}_x\text{Si}$

We report a comprehensive small angle neutron scattering study of the magnetic phase diagram of the doped semiconductor ${\text{Fe}}_{1-x}{\text{Co}}_x\text{Si}$ for $x=0.2$. For magnetic field parallel to the neutron beam we observe a sixfold intensity pattern under field cooling. The regime of the skyrmion lattice is highly hysteretic and extents over a wide temperature range as may be expected due to the site disorder of the Fe and Co atoms. Our study identifies ${\text{Fe}}_{1-x}{\text{Co}}_x\text{Si}$ as the second material in which a skyrmion lattice forms and establishes that skyrmion lattices exist also in doped semiconductors.

Figure 1

(Color online) Typical SANS data of ${\text{Fe}}_{1-x}{\text{Co}}_x\text{Si}$ for $x=0.2$. (A)–(C) Intensity after ZFC. (D) A phase after ZFC for increasing $B$ parallel to the neutron beam. (E)–(G) Sixfold intensity distribution in the A phase after field cooling for $B$ parallel to the neutron beam. (H) A phase after field cooling for $B$ perpendicular to the neutron beam.

Figure 2

(Color online) Magnetic phase diagram of ${\text{Fe}}_{1-x}{\text{Co}}_x\text{Si}$ for $x=0.2$. Gray arrows show the location of temperature and field scans. Red/Gray data points show transition fields and temperatures as determined in these scans. Panels (A)–(C) show the magnetic phase diagrams after ZFC; in the green shaded area the scattering intensity of the ZFC state is observed. Panels (D)–(F) show the magnetic phase diagrams for FC. Across the dark blue/gray area the intensity displays a maximum.

Figure 3

(Color online) Temperature and magnetic field dependences of the integrated scattering intensity. (A) Intensity for $B\parallel ⟨110⟩$ and $B$ perpendicular to the neutron beam. (B) Intensity for $B\parallel ⟨111⟩$ and $B$ parallel to the neutron beam. (C) and (D) Intensity for $B$ parallel to neutron beam under FC. All panels use the same arbitrary scale; gray shading shows the background.