Data for Origin of skyrmion lattice phase splitting in Zn-substituted Cu2OSeO3

We present an investigation into the structural and magnetic properties of Zn-substituted Cu2OSeO3, a system in which the skyrmion lattice (SkL) phase in the magnetic field-temperature phase diagram was previously seen to split as a function of increasing Zn concentration. We find that splitting of the SkL is only observed in polycrystalline samples and reflects the occurrence of several coexisting phases with different Zn content, each distinguished by different magnetic behavior. No such multiphase behavior is observed in single crystal samples. FIG. 2: Powder X-ray diraction peak at 2 theta = 96:65 deg. for polycrystalline samples with different Zn concentrations. Open circles: experimental data; dashed lines: single peak fits for individual phases; gray solid line: a sum of these fits; red line: difference between the global fit and the data. This demonstrates that the asymmetrical shape and splitting of diffraction peaks can only be modelled by multiple phases. FIG. 3: (a) Magnetization M vs T for polycrystalline samples, measured in a magnetic field of 25 mT. (b) The same for single crystal samples. (c) The temperature derivative of the M vs. T for polycrystalline samples, revealing multiple magnetic transitions. (open circles: experientially obtained data, blue, orange and green dotted lines: fits to distinct magnetic phases.) (d) The temperature derivative of the M vs T single crystal data, showing a single transition. FIG. 4: (Top) Critical temperature Tc (crosses) and lattice parameter a (circles) for each Cu2OSeO3 phase in polycrystalline samples, as a function of Zn-substitution. (Bottom) Volume fractions of each distinct phase in polycrystalline samples extracted from X-ray and DC magnetometry data. FIG. 5: (a)-(d) Real component of AC susceptibility ¬chi at a frequency of 10 Hz and driving field of 0.3 mT as a function of field B and temperature T for polycrystalline samples, showing the paramagnetic (P), ferrimagnetic (F), conical (C), helical (H) and skyrmion lattice (S) phases. (e)-(h). The same, but for single crystal samples. FIG. 6:(a) LF muSR spectra for 6.4% Zn-substituted polycrystalline Cu2OSeO3 measured at 54 K in 18 mT on a logarithmic scale with the background subtracted. Lines are guides to the eye. Relaxation rate lambda for LF muSR measurements of (b) pristine, (c) 6.4% and (d) 10.5% Zn-substituted Cu2OSeO3. Shaded regions indicate the location of the SkL phase derived from AC susceptibility.