An experimental technique based on time-resolved Kerr rotation allows a comparison of the spin stiffnesses of different spin-polarized and depolarized states in a two-dimensional electron system. With this technique, a new spin-correlated phase that has no known analogues was discovered. the new spin-depolarized phase is characterized by high spin stiffness equal to that of a spin-polarized quantum Hall ferromagnet.Recently, much attention has been devoted to technological applications based on the manipulation of spin degree of freedom, which has particularly boosted the development of magnonics, the use of spin waves (magnons) for signal transfer 1-3 . More exotic applications entail the involvement of skyrmions, which are spin vortex textures that are topological charge carriers, in spin dynamics. Experimental work on the manipulation of skyrmions and measurement of their mass and characteristic drift length in crossed magnetic and electric fields has been reported 4 .Most of the aforementioned experimental achievements in manipulation of spins and their textures have been for three-dimensional magnetic systems. In contrast, for a two-dimensional electron system (2DES) in a magnetic field, which has given rise to spin-texture physics, the experimental progress is not so impressive. This is largely due to the absence of reliable experimental techniques revealing the local properties of 2DES spin subsystems, such as Lorentz transmission electron microscopy 5 . Setting aside the transport techniques that are not very sensitive to spin ordering, the key method for the characterization of a spin subsystem involves the measurement of the 2DES magnetization as a function of temperature and filling factor and comparison of the experimental data with those obtained from existing theories 6,7 . A quantum Hall ferromagnet (QHF) with a filling factor of ν = 1 is chosen as a reference point of a fully spin-polarized state with maximum achievable spin stiffness. However, for a spin depolarized 2DES, little experimental opportunities for revealing the physical reason for this depolarization exist.A breakthrough in description of spin-depolarized states was achieved when experimentalists focused on the investigation of the spin relaxation processes in a 2DES determined by the local properties of the spin subsystem. The pioneering works on nuclear spin relaxation via a contact interaction with the spins of an electron system led to the concept of skyrmions and skyrmion crystal 8,9,10 . Although the theory of skyrmion crystals was developed for two-dimensional electron systems, the actual formation of a skyrmion crystal lattice was found in three-dimensional MnSi ferromagnetic films and similar compounds with Dzyaloshinskii-Moriya interaction 5,11,12 . Thus far, there has been no compelling evidence on the existence of a skyrmion crystal in a 2DES formed by either lack or excess of electron density in a quantum Hall ferromagnet. Moreover, observations of spin excitation spectra using the inelastic light scattering technique ena...
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