arXiv subjects

V. P. Lesnikov

Publications and source records attributed to V. P. Lesnikov.

8 recordsLinked to original sources

arXiv2020

High-temperature intrinsic ferromagnetism in heavily Fe-doped GaAs layers

The layers of a high-temperature novel GaAs:Fe diluted magnetic semiconductor (DMS) with an average Fe content up to 20 at. % were grown on (001) i-GaAs substrates using a pulsed laser deposition in a vacuum. The transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy investigations revealed that the conductive layers obtained at 180 and 200 C are epitaxial, do not contain any second-phase inclusions, but contain the Fe-enriched columnar regions of overlapped microtwins. The TEM investigations of the non-conductive layer obtained at 250 C revealed the embedded coherent Fe-rich clusters of GaAs:Fe DMS. The X-ray photoelectron spectroscopy investigations showed that Fe atoms form chemical bonds with Ga and As atoms with almost equal probability and thus the comparable number of Fe atoms substitute on Ga and As sites. The n-type conductivity of the obtained conductive GaAs:Fe layers is apparently associated with electron transport in a Fe acceptor impurity band within the GaAs band gap. A hysteretic negative magnetoresistance was observed in the conductive layers up to room temperature. Magnetoresistance measurements point to the out-of-plane magnetic anisotropy of the conductive GaAs:Fe layers related to the presence of the columnar regions. The studies of the magnetic circular dichroism confirm that the layers obtained at 180, 200 and 250 C are intrinsic ferromagnetic semiconductors and the Curie point can reach up to at least room temperature in case of the conductive layer obtained at 200 C. It was suggested that in heavily Fe-doped GaAs layers the ferromagnetism is related to the Zener double exchange between Fe atoms with different valence states via an intermediate As and Ga atom.

physics.app-ph↗

arXiv2019

The formation of epitaxial p-i-n structures on the basis of (In,Fe)Sb and (Ga,Fe)Sb layers

Multilayer structures on the basis of n-type (In,Fe)Sb and p-type (Ga,Fe)Sb diluted magnetic semiconductors (DMS) along with separate (In,Fe)Sb and (Ga,Fe)Sb layers were fabricated on GaAs substrates by pulsed laser sputtering of InSb, GaAs, GaSb, Sb and Fe targets in a vacuum. Transmission electron microscopy and energy-dispersive x-ray spectroscopy reveal a strong dependence of the phase composition of the (In,Fe)Sb compound on the growth temperature. An increase of the latter from 220C to 300C leads to a coalescence of Fe atoms and formation of a secondary crystalline phase in the (In,Fe)Sb layer with a total Fe content of ca. 10 at. %. At the same time, the Ga0.8Fe0.2Sb layers obtained at 220C and 300C are single-phase. The separate In0.8Fe0.2Sb and Ga0.8Fe0.2Sb layers grown on i-GaAs at 220C are DMS with Curie temperatures of ca. 190 K and 170 K, respectively. The three-layer p-i-n diode (In,Fe)Sb/GaAs/(Ga,Fe)Sb structure grown on a GaAs substrate at 220C with a Fe content of ca. 10 at. % in the single-phase (In,Fe)Sb and (Ga,Fe)Sb layers has a rather high crystalline quality and can be considered as a prototype of a bipolar spintronic device based on Fe-doped III-V semiconductors.

physics.app-ph↗

arXiv2019

Robustness of ferromagnetism in (In,Fe)Sb diluted magnetic semiconductor to variation of charge carrier concentration and Fermi level position

The influence of He+ ion irradiation on the transport and magnetic properties of epitaxial layers of a diluted magnetic semiconductor (DMS) (In,Fe)Sb, a two-phase (In,Fe)Sb composite and a nominally undoped InSb semiconductor has been investigated. In all layers, a conductivity type conversion from the initial n-type to the ptype has been found. The ion fluence at which the conversion occurs depends on the Fe concentration in the InSb matrix. Magnetotransport properties of the two-phase (In,Fe)Sb layer are strongly affected by ferromagnetic Fe inclusions. An influence of the number of electrically active radiation defects on the magnetic properties of the single-phase In0.75Fe0.25Sb DMS has been found. At the same time, the results show that the magnetic properties of the In0.75Fe0.25Sb DMS are quite resistant to significant changes of the charge carrier concentration and the Fermi level position. The results confirm a weak interrelation between the ferromagnetism and the charge carrier concentration in (In,Fe)Sb.

cond-mat.mtrl-sci↗

arXiv2018

Magnetic properties, chemical and phase composition of thin manganese silicide films fabricated by pulsed laser deposition

Manganese silicide (MnxSiy) thin films with Mn content (CMn) varied from 24 at. % to 52 at. % were grown on i-GaAs (100) substrates. Chemical, phase composition and room temperature magnetic properties of the films were investigated. It was demonstrated that manganese silicide films revealing ferromagnetic properties are multiphase systems. The phases, which are believed to be non-magnetic at room temperature, are compounds with Mn concentration exceeding the average Mn content of the film (higher manganese silicide, MnSi and Mn5Si3). Magnetic properties revealed are attributed with the secondary phases which are Mn doped silicon (Mn:Si) or Mn depleted compounds. For nearly single phase films (with very small 2-nd phase ratio) no room temperature ferromagnetism was observed.

cond-mat.mes-hall↗

arXiv2017

High-temperature intrinsic ferromagnetism in the (In,Fe)Sb semiconductor

The (In,Fe)Sb layers with the Fe content up to 13 at. % have been grown on (001) GaAs substrates using the pulsed laser deposition. The TEM investigations show that the (In,Fe)Sb layers are epitaxial and free of the inclusions of a second phase. The observation of the hysteretic magnetoresistance curves at temperatures up to 300 K reveals that the Curie point is above room temperature. The resonant character of magnetic circular dichroism confirms the intrinsic ferromagnetism in the (In,Fe)Sb layers. We suggest that the ferromagnetism of the (In,Fe)Sb matrix is not carrier-mediated and apparently is determined by the mechanism of superexchange interaction between Fe atoms (This work was presented at the XXI Symposium Nanophysics and Nanoelectronics, Nizhny Novgorod, March, 13-16, 2017 (book of proceedings v.1, p. 195), http://nanosymp.ru/UserFiles/Symp/2017_v1.pdf).

cond-mat.mtrl-sci↗

arXiv2010

Room temperature ferromagnetism and anomalous Hall effect in Si$_{1-x}$Mn$_x$ ($x\approx 0.35$) alloys

A detailed study of the magnetic and transport properties of Si$_{1-x}$Mn$_x$ ($x\approx 0.35$) films is presented. We observe the anomalous Hall effect (AHE) in these films up to room temperature. The results of the magnetic measurements and the AHE data are consistent and demonstrate the existence of long-range ferromagnetic (FM) order in the systems under study. A correlation of the AHE and the magnetic properties of Si$_{1-x}$Mn$_x$ ($x\approx 0.35$) films with their conductivity and substrate type is shown. A theoretical model based on the idea of a two-phase magnetic material, in which molecular clusters with localized magnetic moments are embedded in the matrix of a weak itinerant ferromagnet, is discussed. The long-range ferromagnetic order at high temperatures is mainly due to the Stoner enhancement of the exchange coupling between clusters through thermal spin fluctuations (paramagnons) in the matrix. Theoretical predictions and experimental data are in good qualitative agreement.

cond-mat.mes-hall↗

arXiv2010

Room temperature ferromagnetism and anomalous Hall effect in Si_{1-x}Mn_x (x = 0.35) alloys

A detailed study of the magnetic and transport properties of Si1-xMnx (X = 0.35) films is presented. We observe the anomalous Hall effect (AHE) in these films up to room temperature. The results of the magnetic measurements and the AHE data are consistent and demonstrate the existence of long-range ferromagnetic (FM) order in the systems under study. A correlation of the AHE and the magnetic properties of Si1-xMnx (X = 0.35) films with their conductivity and substrate type is shown. A theoretical model based on the idea of a two-phase magnetic material, in which molecular clusters with localized magnetic moments are embedded in the matrix of a weak itinerant ferromagnet, is discussed. The long-range ferromagnetic order at high temperatures is mainly due to the Stoner enhancement of the exchange coupling between clusters through thermal spin fluctuations ("paramagnons") in the matrix. Theoretical predictions and experimental data are in good qualitative agreement.

cond-mat.mes-hall↗

arXiv2006

Peculiarities of the transport properties of InMnAs layers, produced by the laser deposition, in strong magnetic fields

Magnetotransport properties of p-InMnAs layers are studied in pulsed magnetic fields up to 30 T. Samples were prepared by the laser deposition and annealed by ruby laser pulses. Well annealed samples show p-type conductivity while they were n-type before the annealing. Surprisingly the anomalous Hall effect resistance in paramagnetic state (T>40 K) and in strong magnetic fields (B > 20 T) appears to be greater than that in ferromagnetic state (T <= 40 K), while the longitudinal resistance rises with the temperature decrease. The negative magnetoresistance saturates in magnetic fields higher then 10T at T near 4 K only, whereas the saturation fields of the anomalous Hall effect resistance are much less (around 2 T at 30K). The total reduction of resistance exceeds 10 times in magnetic fields around of 10T. The obtained results are interpreted on the base of the assumptions of the non-uniform distribution of Mn atoms acting as acceptors, the local ferromagnetic transition and the percolation-like character of the film conductivity, which prevailed under conditions of the strong fluctuations of the exchange interaction. Characteristic scales of the magneto-electric nonuniformity are estimated using analysis of the mesoscopic fluctuations of the non-diagonal components of the magnetoresistivity tensor.

cond-mat.mtrl-sci↗