Ferromagnetic-paramagnetic transition in p-Si/SiGe due to Landau levels overlapping

The magnetoresistance $\rho_{xx}$ and $\rho_{xy}$ as well as attenuation and velocity change of surface acoustic waves were measured in a p-Si/SiGe sample with $p$=2$\times$10$^{11}$\,cm$^ {-2}$. The research was performed in the temperature range of 0.3-2 K and in the magnetic fields of up to 18 T tilted with respect to the two-dimensional (2D) channel plane. The dependence of the g-factor g*($\Theta$)/g*($0^{\circ}$) on the tilt angle was determined. The measurements of $\rho_{xx}$ and $\rho_{xy}$ in the tilted magnetic field showed that the anomaly in $\rho_{xx}$ observed at filling factor $\nu$ =3/2 is insignificant in the conductivity $\sigma_{xx}$. The anomaly in $\sigma_{xx}$ at $\nu$ =2 might be explained by overlapping of the levels with different spins 0$\uparrow$ and 1$\downarrow$ when the tilt angle of the applied magnetic field is changed. The overlapping occurs at $\Theta$ of about $60^{\circ}$ and causes a ferromagnetic-paramagnetic transition.