Pecularities of Hall effect in GaAs/δMn/GaAs/In _xGa _(1-x)As/ GaAs (x ≈ 0.2) heterostructures with high Mn content

摘要

The transport properties of GaAs/δMn/GaAs/In _xGa _(1-x)As/ GaAs (x ≈ 0.2) quantum well (QW) and a Mn delta layer (DL) with relatively high content, about one Mn monolayer (ML), are studied. In these structures the DL is separated from the QW by GaAs spacer with thickness ds = 2-5 nm. All structures possess a non-metallic character of conductivity and display a maximum in the resistance temperature dependence Rxx(T) at the temperature ≈46 K, which is usually associated with the Curie temperature TC of ferromagnetic (FM) transition in DL. However, it is found that the Hall effect concentration of holes pH in the QW does not decrease below TC as one ordinary expects in similar systems. On the contrary, the dependence pH(T) experiences a minimum at T = 80-100 K depending on the spacer thickness, then increases at low temperatures more strongly when ds is smaller, and reaches a giant value pH = (1-2) × 1013 cm-2. The obtained results are interpreted in the terms of magnetic proximity effect of the DL on the QW, inducing spin polarization of the holes in the QW. Strong structural and magnetic disorder in the DL and in the QW, leading to phase segregation in them is taken into consideration. The high pH value is explained as a result of the compensation of the positive normal Hall effect component by the negative anomalous Hall effect component.