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Scheme of the structures. Ten nanometres wide (In,Ga)As quantum well (QW) is set apart from the ferromagnetic 1 nm thick (Ga,Mn)As layer by GaAs barrier with the thickness nm. (b) Single-beam magneto-optical Kerr rotation for the ‘10 nm’ sample measured in Faraday geometry. The mutual orientation of magnetic field, sample, and incident and reflected light is schematically shown in the inset. The photon energy is eV. K.
Source publication
The spin orientation of electrons is studied in ferromagnet (FM)–semiconductor (SC) hybrid structures composed of a (Ga,Mn)As ferromagnetic layer, which is placed in the direct vicinity of a non‐magnetic SC quantum well (QW). It is shown that the polarization of carriers in the SC QW is achieved by spin‐dependent tunnelling into the magnetized ferr...
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Context 1
... experiments were carried out on GaAs-based structures, whose design is schematically shown in Fig. 2a. The Mn layer is separated from the 10 nm wide (In,Ga)As QW with about 10% of In content by a 5 or 10 nm thick spacer. In the following, we will label the samples according to this spacer thickness d s , '5 nm' and '10 nm', respectively. Due to diffusion of Mn ions, the layer is transformed into an ≈1 nm thick ferromagnetic layer of Ga ...
Context 2
... rotation angle of the polarization plane of the reflected beam is proportional to the magnetization z-axis component M z . The signal is homodyne detected using a polarization bridge in combination with a balanced photodiode and a lock-in amplifier. The typical magnetization curve at the temperature T = 2 K for the '10 nm' sample is presented in Fig. 2b. It shows a hysteresis loop with coercive field B c ∼ 10-20 mT. The form of the magnetization curve and the value of B c are independent of the photon energy of the incident beam in the wide range from 1.4 to 1.8 eV. This indicates that the MOKE signal originates from the FM layer rather than the QW. Figure 3a shows the PL spectrum ...
Context 3
... the PL polarization is absent. Figure 3b shows the polarization hysteresis loop ρ c (B), measured at the PL maximum under linearly polarized excitation. The coercive force is determined to be B c ≈ 10 mT, and the polarization loop closes approximately at the magnetic field of 60 mT. The shape of the hysteresis loop is similar to the MOKE data in Fig. 2b. Hence, the appearance of hysteresis demonstrates that the polarization degree of QW emission is controlled by the (Ga,Mn)As FM layer. The excitation photon energy ω exc = 1.44 eV, which corresponds to quasi-resonant below-barrier excitation of the QW. This allows us to perform excitation and detection through the GaAs substrate in ...
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Citations
... To magnetize the FM layer a magnetic field B = 100 mT is applied to the sample in Faraday geometry (the magnetic field is parallel to the optical axis and structure growth axis; see Figure 1). 5 The photo-EMF spectrum reaches its maximum of 0.8 mV at excitation energy ℏω exc = 1.421 eV. The maximum of the spin-photo-EMF spectrum is approximately 10 times smaller and reaches 0.07 mV under the same excitation energy. ...
Hybrid structures combining ferromagnetic (FM) and semiconductor constituents have great potential for future applications in the field of spintronics. A systematic approach to study spin-dependent transport in a GaMnAs/GaAs/InGaAs quantum well (QW) hybrid structure with a few-nanometer-thick GaAs barrier is developed. It is demonstrated that a combination of spin electromotive force measurements and photoluminescence detection provides a powerful tool for studying the properties of such hybrid structures and allows the resolution of the dynamic FM proximity effect on a nanometer scale. The method can be generalized to various systems, including rapidly developing 2D van der Waals materials.
... To magnetize the FM layer magnetic field B = 100 mT is applied to the sample in Faraday geometry (magnetic field is parallel to the optical axis and structure growth axis, see Fig. 1). 5 The photo-EMF spectrum reaches its maximum of 0.8 mV at excitation energy ω exc = 1.421 eV. The maximum of the spin-photo-EMF spectrum is approximately 10 times smaller and reaches 0.07 mV under the same excitation energy. ...
Hybrid structures combining ferromagnetic (FM) and semiconductor constituents have great potential for future applications in the field of spintronics. A systematic approach to study spin-dependent transport in the GaMnAs/GaAs/InGaAs quantum well (QW) hybrid structure with a few nanometer thick GaAs barrier is developed. It is demonstrated that a combination of spin electromotive force measurements and photoluminescence detection provides a powerful tool for studying the properties of such hybrid structures and allows to resolve the dynamic FM proximity effect on a nanometer scale. The method can be generalized on various systems including rapidly developing 2D van der Waals materials.
... Second, control of the spin dynamics of carriers (control of their magnetization) can be efficiently provided in hybrid structures [14,[17][18][19]. There are various types of such structures composed of different materials, for example, two semiconductor layers separated by a ferromagnetic layer; a ferromagnetic layer and a semiconductor quantum well (QW), separated by a nanometer-thick barrier; two coupled QWs of different widths separated by a thin barrier, where one QW contains magnetic ions. ...
The coherent spin dynamics of electrons in tunnel-coupled CdTe and (Cd,Mn)Te quantum wells (QWs) is studied by time-resolved pump-probe Kerr rotation. The coupled QWs have different thicknesses; the narrow one is doped by Mn2+ magnetic ions. A short range proximity effect between them is observed: the Zeeman splitting of electrons in the wide QW is given in addition to the intrinsic electron g factor by the exchange interaction with the Mn2+ ions mediated by electron tunneling into the narrow QW. The exchange interaction strength scales with the Cd0.88Mg0.12Te barrier thickness separating the QWs. The Kerr rotation signal measured on the wide QW shows two close frequencies of electron spin Larmor precession in a transverse magnetic field. These components have very different spin dephasing times, 50 ps and 1 ns. The two frequencies originate from electrons in the wide QW being either part of an exciton or being resident. The proximity effect of the exciton electron is smaller due to the binding by Coulomb interaction, which decreases the tunneling to the narrow well. The experimental data are in good agreement with model calculations.
... The time-dependent Kerr signal shown in Fig. 1c essentially has two oscillations and two exponential decays arising from electron and hole decoherence [11][12][13] . The following equation was used to fit experimental data: www.nature.com/scientificreports ...
... The first indication that electrons do not significantly affect Mn alignment is that the linear increase of the effective magnetic field is not influenced by the exponential decay of the spin coherence. The assumption that the exchange interaction of the electrons on the Mn spins is not of sufficient strength to affect Mn alignment would explain the inconsistencies observed in previous reports [11][12][13] . ...
... These two process mechanisms (Mn spin orientation with pump and further relaxation) occur at different velocities. This can explain inconsistencies observed in previous studies of the same sample between Kerr rotation and photoluminescence results [11][12][13] , where the Mn field strength, obtained by Kerr rotation frequency when the magnetic field tends to zero, is not sufficiently strong to explain the magnetization of the sample, measured by photoluminescence. ...
Time-resolved Kerr rotation measurements were performed in InGaAs/GaAs quantum wells nearby a doped Mn delta layer. Our magneto-optical results show a typical time evolution of the optically-oriented electron spin in the quantum well. Surprisingly, this is strongly affected by the Mn spins, resulting in an increase of the spin precession frequency in time. This increase is attributed to the variation in the effective magnetic field induced by the dynamical relaxation of the Mn spins. Two processes are observed during electron spin precession: a quasi-instantaneous alignment of the Mn spins with photo-excited holes, followed by a slow alignment of Mn spins with the external transverse magnetic field. The first process leads to an equilibrium state imprinted in the initial precession frequency, which depends on pump power, while the second process promotes a linear frequency increase, with acceleration depending on temperature and external magnetic field. This observation yields new information about exchange process dynamics and on the possibility of constructing spin memories, which can rapidly respond to light while retaining information for a longer period.
We theoretically investigate the effect of a δ-potential to a temporal spin splitter for electron in a semiconductor magnetic quantum microstructure (SMQM), which is realized by patterning a perpendicularly-magnetized ferromagnetic stripe on top of InAs/AlxIn1-xAs. The dwell time for electron in the δ-doped SMQM is still spin polarized, because electron spin interacts with structural magnetic field. The spin-dependent dwell time is modulated by switching the δ-potential owing to the dependence of effective potential felt by electron on the δ-doping. These significant findings demonstrate that such a δ-doped SMQM acts as a manipulable temporal electron-spin splitter, which may be helpful for design of spintronic devices.
The GaAs/InGaAs quantum wells with a ferromagnetic δ〈Mn〉 layer in GaAs barrier demonstrate a set of interesting spin-related phenomena originating from Mn-hole interaction. One of such phenomena is a spin-memory effect which consists of Mn spin polarization induced by interaction with vicinity spin-polarized holes generated under the exposure by short circularly polarized light pulses. Here long Mn spin relaxation time (∼5 ns) allows preserving the spin polarization of the entire system. In the present paper the spin-memory effect investigation was carried out by analyzing the polarization kinetics of quantum-well photoluminescence in the pump-probe technique. It was shown that the photoluminescence circular polarization degree is strongly affected by the magnetic interaction of holes with Mn atoms prepolarized by the pump pulse. In the case of antiparallel Mn and hole polarizations, magnetic interaction leads to decrease of circular polarization degree as compared with single-pulse excitation (so called ΔP effect). Interestingly, the amplitude of hole-mediated ΔP effect is strongly affected by the concentration of resident electrons in the quantum well. The latter was shown to be caused by the specific compliance with selection rules for optical transitions with the participation of unpolarized resident electrons and spin-polarized holes affected by Mn-hole interaction.
