Electron spin resonance in an AlAs quantum well near filling factor 1

The phenomenon of spin resonance of two-dimensional electrons confined in a 16 nm AlAs quantum well is studied in the quantum Hall effect regime near filling factor $1$. At a temperature of $T = 0.5$K, spin resonance is not observed directly at filling factor $\nu = 1$, but it is found already with slight deviation from it and at the increase in the temperature of the sample. The dependence of the resonance amplitude on the filling factor has two maxima near filling factors $\nu \approx 0.9$, $1.1$ symmetric with respect to $\nu = 1$. The temperature dependences of the spin resonance amplitude near different filling factors are studied. It occurs that the resonance amplitude decreases with decreasing temperature $T$ directly at filling factor $1$. With deviation from it, the character of the temperature dependence changes. At $\nu\approx 0.9,1.1$, the electron paramagnetic resonance amplitude increases with decreasing $T$. Near filling factor $1$, the temperature dependence of the amplitude is with good accuracy proportional to the temperature derivative of the longitudinal magnetoresistance measured at the same. However, quantitative agreement is violated when $\nu\ne 1$.These experimental observations indicate that the detection of spin resonance at filling factor $1$ is based on the sensitivity of the longitudinal magnetoresistance to heating caused by the resonant absorption of microwave radiation, but this mechanism no longer works when $\nu\ne 1$.