We describe a technique for online control of the reliability of the data of magnetic circular dichroism spectroscopy in reflected light, which is based on measuring the polar magneto-optical Kerr effect under normal incidence of light on a sample with a method of phase modulation of a light wave using a photoelastic modulator. The presented technique involves measuring the amplitudes of signals at the “zero” ( V = ) and doubled ( V 2 f ) frequency f of the retardation modulation in crossed polarizers in the process of scanning over a spectrum. In these measurements, the constancy of the V 2 f / V = ratio over the entire spectral range confirms the reliability of the spectroscopy data. The possible instrumental errors that lead to a distortion of the recorded spectrum shape were analyzed. The operability and efficiency of the technique is illustrated by an example of measuring the magnetic circular dichroism spectrum of a MnAs film.

The spectral, temperature, and magnetic field dependences of the magneto-optical transversal Kerr effect (TKE) have been studied along with the optical spectra of InFeAs layers formed by ion implantation with further pulsed laser melting at different laser pulse energies. A strong dependence of the magneto-optical and optical properties of InFeAs layers on the pulse energy has been revealed. The TKE spectra of the specimen formed at a minimum pulse energy ( W = 0.1 J/cm 2 ) indicate the presence of ferromagnetic (In, Fe)As nanoclusters with a Curie temperature of ≈180 K in the weakly doped semiconductive matrix and the absence of secondary magnetic phases. The TKE spectra of layers formed at W = 0.15–0.4 J/cm 2 are a superposition of the contributions from ferromagnetic (In,Fe)As nanoareas distributed in the volume and near-surface Fe inclusions. The predominance of the iron contribution in the spectra indicates the intensification of Fe diffusion towards the surface with an increase in the laser pulse energy. Anisotropy in the magneto-optical and optical spectra confirms anisotropic chemical phase separation in the layers.

Abstract—Spectral and temperature dependences of the magneto-optical transversal Kerr effect (TKE) of GaMnAs layers prepared by different methods are reported in this work. The GaMnAs layers prepared by pulsed laser sputtering at 300°С demonstrate a ferromagnetic behavior below 80 K, which is due to the presence of local ferromagnetic (Ga,Mn)As areas in the paramagnetic matrix. The Ga(In)MnAs layers prepared by ion implantation and subsequent pulsed laser annealing were found to exhibit a high TKE response at low temperatures. The presence of the characteristic band in the TKE spectrum in the range of transitions near the L point of the band structure of Ga(In)As confirms the intrinsic ferromagnetism. The temperature dependences of TKE measured for different spectrum ranges demonstrate nonmonotonic behavior, which indicates the magnetic inhomogeneity of the layers. The peculiarities of the magneto-optical spectra of GaMnAs, which were not observed previously, were explained by taking the magnetic and phase inhomogeneity of the layers into account. The sensitivity of TKE to the phase inhomogeneity of the Ga(In)MnAs layers and the efficiency of TKE in studying the electron spectrum and magnetic structure of diluted magnetic superconductors are demonstrated.

AbstractIn this paper, we present the results of studies of the spectral, temperature, and field dependences of the transversal Kerr effect in Ga_1 – _ x Mn_ x As ( x = 0.0066–0.033) layers produced by ion implantation and subsequent pulsed laser annealing. The complicated nonmonotonous nature of the temperature dependences of the transversal Kerr effect and its dependence on the measurement range indicate a magnetic inhomogeneity of the layers. The reasons for the inhomogeneity can be the Gaussian distribution of Mn over the thickness of the layers and the electron phase separation in them. The appearance of new features in the spectra of the transversal Kerr effect is explained by the presence in the doped semiconductor matrix of nanoregions with a higher carrier concentration and a higher Curie temperature and a shift of the Fermi level into the valence band leading to an increase in the energy of optical transitions.

In this paper, we present the results of studies of the spectral, temperature, and field dependences of the transversal Kerr effect in Ga1 – xMnxAs (x = 0.0066–0.033) layers produced by ion implantation and subsequent pulsed laser annealing. The complicated nonmonotonous nature of the temperature dependences of the transversal Kerr effect and its dependence on the measurement range indicate a magnetic inhomogeneity of the layers. The reasons for the inhomogeneity can be the Gaussian distribution of Mn over the thickness of the layers and the electron phase separation in them. The appearance of new features in the spectra of the transversal Kerr effect is explained by the presence in the doped semiconductor matrix of nanoregions with a higher carrier concentration and a higher Curie temperature and a shift of the Fermi level into the valence band leading to an increase in the energy of optical transitions.

Abstract—Layers of InAs, InSb, and GaSb semiconductors highly doped with iron during their growth by the method of pulsed laser deposition are studied experimentally. The best temperatures for layer formation on GaAs (100) substrates are: 250°C (InSb : Fe), 300°C (InAs : Fe), and 350°C (GaSb : Fe). At high Fe concentration (over 10 at %) the layers display ferromagnetic properties expressed in emergence of a hysteresis curve within the magnetic field dependences of the Hall resistance, negative magnetoresistance, and in some cases, ferromagnetic-type magnetization at measurements at room temperature. The atoms of iron do not change the type of layer conductivity; InAs : Fe and InSb : Fe layers possess n-type conductivity, and GaSb : Fe layers display p-type conductivity due to their intrinsic point defects.

GaMnAs layers grown by pulsed laser deposition were studied by magneto-optical transversal Kerr effect spectroscopy, spectral ellipsometry, resistivity and the Hall effect measurements, and magnetometry. The growth regimes for magnetically inhomogeneous layers containing Mn-enriched ferromagnetic regions with different composition and sizes were established. The layers grown at a temperature of 300°C exhibit a ferromagnetic behavior at temperatures below 80 K, which is conditioned by the presence of local ferromagnetic (Ga,Mn)As regions in the paramagnetic matrix. The nature of peculiarities in the TKE spectrum of these layers is discussed.

Ga-1 xMnxAs layers prepared by ion implantation and subsequent pulsed laser annealing with the planned Mn concentrations of x = 0.01-0.08 have been studied using the magneto-optical transversal Kerr effect (TKE) and spectral ellipsometry. The spectral dependences of the diagonal and nondiagonal components of the permittivity tensor (PT), as well as the spectrum of magnetic circular dichroism (MCD) have been calculated for the layers. The obtained spectra of the diagonal PT components show that the layers under study maintain the zinc-blende crystal structure of the parent GaAs semiconductor. All studied samples reveal a strong TKE response at low temperatures with a dependence of an effective Curie temperature (at which TKE appears) on the Mn concentration. A number of extrema in the low-temperature TKE and MCD spectra are close to the energies of transitions in the Gamma and L critical points of the parent semiconductor band structure that confirms the intrinsic ferromagnetism of the Ga-1 xMnxAs layers. The MCD spectra shape and its change with Mn concentration increasing are discussed on a base of the valence-band model of ferromagnetism in DMS. (C) 2017 Published by Elsevier B.V.

AbstractGaMnAs layers grown by pulsed laser deposition were studied by magneto-optical transversal Kerr effect spectroscopy, spectral ellipsometry, resistivity and the Hall effect measurements, and magnetometry. The growth regimes for magnetically inhomogeneous layers containing Mn-enriched ferromagnetic regions with different composition and sizes were established. The layers grown at a temperature of 300°C exhibit a ferromagnetic behavior at temperatures below 80 K, which is conditioned by the presence of local ferromagnetic (Ga,Mn)As regions in the paramagnetic matrix. The nature of peculiarities in the TKE spectrum of these layers is discussed.

Abstract —Layers of InAs, InSb, and GaSb semiconductors highly doped with iron during their growth by the method of pulsed laser deposition are studied experimentally. The best temperatures for layer formation on GaAs (100) substrates are: 250°C (InSb : Fe), 300°C (InAs : Fe), and 350°C (GaSb : Fe). At high Fe concentration (over 10 at %) the layers display ferromagnetic properties expressed in emergence of a hysteresis curve within the magnetic field dependences of the Hall resistance, negative magnetoresistance, and in some cases, ferromagnetic-type magnetization at measurements at room temperature. The atoms of iron do not change the type of layer conductivity; InAs : Fe and InSb : Fe layers possess n -type conductivity, and GaSb : Fe layers display p -type conductivity due to their intrinsic point defects.

GaMnAs layers fabricated on GaAs(001) substrates by laser ablation technique were studied using the magneto-optical transversal Kerr effect (TKE) (E = 0.5 - 4.0 eV) and spectral ellipsometry (E = 1.4 - 4.5 eV). Obtained spectral, temperature and magnetic field TKE dependences shown that the used technique allowed us to obtain ferromagnetic (Ga,Mn)As layers, whose composition was close to single-phase one (without MnAs inclusions). Spectral dependences of the off-diagonal components (e’ = e’1 - ie’2) of the permittivity tensor and also of the magnetic circular dichroism (MCD) were calculated for ferromagnetic (Ga,Mn)As sample. The calculated dependences were compared with the published magneto-optical spectra of (Ga,Mn)As layers grown by molecular beam epitaxy.

Optical and magneto-optical properties of GaMnSb layers fabricated on GaAs (001) substrates by laser ablation technique were studied using spectral ellipsometry (E =1.24-3.25 eV) and the transversal Kerr effect (TKE) (E = 0.5 4.2 eV) as well as atomic and magnetic force microscopy. Spectra of the constituents of the diagonal components of the permittivity tensor as well as TKE depended substantially on the layer fabrication conditions. At room temperature a strong resonant band was observed in the TKE spectra for the GaMnSb layers with low Mn content in the energy range E 0.5-1.5 eV. This resonant TKE band was explained by excitation of surface plasmons in MnSb nanoclusters, which arose during the growth of the layers. In the energy region E >1.5 eV the TKE spectra were related to interband transitions in MnSb inclusions.

Optical and magneto-optical properties of In(Ga)MnAs layers fabricated by laser ablation on GaAs(100) substrates were studied. Spectra of the optical constants and the transversal Kerr effect (TKE) depended substantially on the conditions of layer fabrication and testified to the presence of MnAs inclusions in all the samples. The cross-sectional transmission electron microscopy revealed the presence in the layers of inclusions 10-40 nm in size. At room temperature, a strong resonant band was observed in the TKE spectra of some In(Ga)MnAs layers in the energy range 0.5-2.7 eV. The resonant character of the TKE spectra was explained by excitation of surface plasmons in the MnAs nanoclusters embedded in the semiconductor host.

Spectral dependences of the transversal Kerr effect (TKE) as well as of the real and imaginary parts of the permittivity of InMnAs layers were studied. Pulsed laser ablation of Mn and InAs targets was used to form the layers on GaAs(100) substrates. Spectra of the optical constants and TKE depended substantially on layer fabrication conditions and testified to the presence of MnAs inclusions in the samples. The cross-sectional transmission electron microscopy revealed the presence of inclusions of size 10-40 nm in the layers. At room temperature a strong resonant band was observed in the TKE spectra of the InMnAs layers in the energy range of 0.5-2.2 eV. In this band the TKE was comparable in magnitude but opposite in sign to that in the strong ferromagnetic MnAs. The resonant character of the TKE spectra was explained by excitation of surface plasmons in the MnAs nanoclusters embedded in the InMnAs semiconductor host. Modelling the TKE spectra for (InAs)(1-X):(MnAs)(X) nanocomposites in the effective-medium approximation (Maxwell-Garnett approximation) confirmed the assumption on the plasmon mechanism of the resonant enhancement of the transversal Kerr effect in the InMnAs layers.

Spectral dependences of the refractive n(hν) and absorption k(hν) indices (hν= 1.2–4.4 eV) and the magneto-optical constant δ(hν) (hν = 0.5–4.4 eV) of the transverse Kerr effect of the InMnAs layers produced by laser deposition have been studied. The spectra of the diagonal ɛ(hν) and off-diagonal ɛ′hν) components of the permittivity tensor of the layers have been found. A comparison of the spectral dependences δ(hν), ɛ′(hν) and ɛ′2 × (hν)2 of the InMnAs and MnAs layers have been performed. Features in the spectra of the InMnAs layers have been attributed to a competition between the contributions of the In1 − x Mn x As matrix and MnAs inclusions.

Spectral dependences of refractive and absorption indices n(hν), k(hν) (hν=1.2–4.4eV) and the transversal Kerr effect δ(hν) (hν=0.5–4.4eV) in In(Ga)MnAs layers fabricated by laser deposition have been investigated. Spectra of the diagonal and off-diagonal components of the dielectric permittivity tensor of these layers have been calculated. Comparison of the spectral dependences δ(hν), ε′(hν) and ε′2×(hν)2 of the In(Ga)MnAs layers with similar spectra for MnAs has been carried out. Particular features in the spectra of the In(Ga)MnAs layers have been explained by a competition of contributions of the In1−x(Ga1−x)MnxAs host and MnAs inclusions.