Eur. Phys. J. B (2012) 85: 206
https://doi.org/10.1140/epjb/e2012-30149-4

Regular Article

Pecularities of Hall effect in GaAs/δ⟨Mn⟩/GaAs/In_xGa_1-xAs/ GaAs (x ≈ 0.2) heterostructures with high Mn content

¹ Russian Research Centre “Kurchatov Institute”, 123182 Moscow, Russia
² Institute of Applied and Theoretical Electrodynamics, Russian Academy of Sciences, 127412 Moscow, Russia
³ Dipartimento di Fisica, Università di Roma “La Sapienza”, piazzale Aldo Moro, 2- 00185 Roma, Italy
⁴ Institute of Physics and Technology of RAS, Nakhimovskii Avenue 34, 117218 Moscow, Russia
⁵ Lappeenranta University of Technology, Box 20, 53851 Lappeenranta, Finland
⁶ Kotel’nikov Institute of Radio Engineering and Electronics, RAS, Fryazino, 141190 Moscow District, Russia

^a e-mail: sergio.caprara@roma1.infn.it

Received: 19 February 2012
Received in final form: 20 April 2012
Published online: 20 June 2012

Abstract

The transport properties of GaAs/δ⟨Mn⟩/GaAs/In_xGa_1−xAs/GaAs structures containing an In_xGa_1−xAs (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 d_s = 2–5 nm. All structures possess a non-metallic character of conductivity and display a maximum in the resistance temperature dependence R_xx(T) at the temperature  ≈ 46 K, which is usually associated with the Curie temperature T_C of ferromagnetic (FM) transition in DL. However, it is found that the Hall effect concentration of holes p_H in the QW does not decrease below T_C as one ordinary expects in similar systems. On the contrary, the dependence p_H(T) experiences a minimum at T = 80–100 K depending on the spacer thickness, then increases at low temperatures more strongly when d_s is smaller, and reaches a giant value p_H = (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 p_H value is explained as a result of the compensation of the positive normal Hall effect component by the negative anomalous Hall effect component.