Evolution of the spin order in Hall ferromagnets under the strong mixing of Landau levels and at the filling factors $1\leqslant\nu\leqslant2$

An unconventional behavior of the spin order in strongly correlated two-dimensional electron systems based on MgZnO/ZnO heterostructures has been detected in the quantum limit at the filling factors $1\leqslant\nu\leqslant2$. Under the variation of the filling factor and the orientation of a magnetic field, inelastic light scattering spectra exhibit characteristic transformations of collective spin excitations, which indicate qualitatively different rearrangements of the spin configuration in the system: smooth depolarization at $1<\nu< 3/2$ with the formation of spin textures and sharp ferromagnetic instability at a certain filling factor in the range $3/2 <\nu\leqslant 2$. Comparison with the magnetotransport experiments reported in [J. Falson, D. Maryenko, B. Friess, et al., Nature Phys. 11, 347 (2015)] shows that the disappearance of spin textures under the variation of the field tilt angle correlates with the appearance of an incompressible state at $\nu = 3/2$.