Magnetic ordering effects in a Mn-modulation-doped high mobility two-dimensional hole system

Abstract

We have studied the magnetotransport properties of a manganese ͑Mn͒-modulation-doped high mobility two-dimensional hole system in a strained InAs quantum well ͑QW͒ structure. At precisely T = 600 mK a phase transition from paramagnetism to ferromagnetism can be observed by a change of the low-field magnetotransport behavior and hysteresis. In the magnetically ordered phase a superposition of positive magnetoresistance and weak antilocalization was detected in the longitudinal resistance R xx and in the Hall resistance R xy a superposition of normal, anomalous, and planar Hall effects demonstrating spontaneous magnetization in the QW plane was detected. From extensive analysis of the temperature and magnetic field dependence of the Shubnikov-de Haas oscillations we deduce the effective mass, transport, and quantum-scattering times. The latter indicates presence of small-range scattering potential. From corrections to the Drude conductivity we determine the impurity interaction time, which is significantly reduced in the ferromagnetic phase indicating interaction of the two-dimensional free holes' spin with the localized magnetic moments of 5/2 from Mn ions.

Spin-polarized electric currents in diluted magnetic semiconductor heterostructures induced by terahertz and microwave radiation

“…This further verifies the interpretation of earlier magnetotransport experiments. 41 Similarly to II-VI DMS samples A1 and A2, we observed that in the inverted sample B1 the magnitude of the photocurrent measured at 1.8 K is about two orders of magnitude larger than that at 40 K. Such enhancement is larger than that expected for the giant Zeeman spin splitting and provides an indirect evidence for the substantial contribution of the photocurrent due to scattering by magnetic ions. However, the direct comparison of the current variation to the Zeeman spin splitting is impossible because no PL or time-resolved Kerr rotation data for the InAs-based QWs are in our disposal.…”

“…41,46 Concerning n-type In(Mn)As DMS, only thin films and superlattices with mobilities in the order of 100 to 1000 cm 2 /Vs have been reported so far. [47][48][49][50] The realization of n-type InAs-based DMS QWs with high mobility and controllable exchange interaction remains an important issue.…”

Magnetooptical study of Zeeman effect in Mn modulation-doped InAs/InGaAs/InAlAs quantum well structures

“…The high quality of the samples becomes, however, obvious at high magnetic fields where the same structures shows well defined quantum Hall steps and Shubnikov de Haas oscillations. 9,17,18 In addition to Mn doped QW samples A and B, an intentionally undoped structure R without any Mn implementation was grown to serve as a reference.…”

Strong localization effect in magnetic two-dimensional hole systems

“…A significant amount of Mn ions is formed in inverted Mn doped heterostructures due to an asymmetric broadening of the doping layer as confirmed by secondary ion mass spectroscopy. 8 The Mn content in the QW is reported to be about 1% of the concentration in the doping layer, which is below 2 ϫ 10 20 cm −3 . We found similar localization effects indicated by NMR in a nonmagnetic carbon ͑C͒ modulation and additional Mn co-doped InAs QW structure demonstrating localization of 2D holes on Mn ions in close vicinity to be responsible for the peculiar low-field magnetotransport behavior.…”

“…6,7 Moreover, Mn modulation-doped InAs-based heterostructures provide the possibility to study the interplay of localized magnetic moments of S = 5 / 2 with spins of highmobility hole systems. 8,9 Furthermore, modulation doping results in higher charge carrier mobilities compared to conventional diluted magnetic semiconductors ͑DMS͒ such as GaMnAs or InMnAs, which are only metallic for very high densities of magnetic impurities. 1 Huge negative magnetoresistance ͑NMR͒ associated with a magnetic-field induced insulator-to-metal transition, which are characteristic features of magnetic semiconductors, 2,3,5,10 were reported for inverted Mn modulation doped two-dimensional hole gases ͑2DHGs͒.…”