Magnetism in manganese modulation-doped two-dimensional hole systems

Diluted magnetic semiconductors on the one hand and two-dimensional carrier systems with strong spin-orbit-coupling on the other hand have been of increasing interest over the past few years. Here we present magnetization measurements on a Mn-modulation doped InGaAs/InAs quantum well at 400 mK in external magnetic fields of up to 15 T. For the measurements a Micromechanical Cantilever Magnetometer (MCM) mounted on a rotational stage was employed. This allows the variation of the tilt angle between the sample magnetization and the external magnetic field. The measurements show a fourfold anisotropy and a hysteretic behavior of the magnetization around B=0. This may be associated with the coupling of the free holes to the magnetic moments of the Mn dopants. An oscillatory behavior that was observed in high magnetic fields could be interpreted as the de Haas-van Alphen effect of the free holes. We present magnetization measurements of a with manganese modulation doped InGaAs InAs InGaAs quantum well heterostructure. The magnetization shows a strong angular dependence at 400 mK at magnetic fields up to 14 T which was further investigated using a micromechanical cantilever magnetometer mounted on a rotational stage. The samples exhibit a fourfold symmetry suggesting a ordered magnetic behavior with symmetry axis at degrees tilt angle between external field and the sample normal. This suggests ferromagnetic behavior. Also, a de Haas-van Alphen (dHvA) oscillation was observed at low temperatures. A filling factor of ν=2 was found at approx. 10 T, which is in good agreement with transport measurements. The influence of sample illumination on the dHvA oscillations was studied.