I. V. Fedorchenko

Manufacture of magnetic granular structures in semiconductor-ferromagnet systems

The requirements are formulated to be fulfilled by magnetic granular structures that have the giant magnetoresistance (GMR) in semiconductor-ferromagnet systems. AIIBIVC2V-Mn(CV), AIIICV-Mn(CV), and A3IIC2V-Mn(CV) semiconductor-ferromagnet systems are shown to be eutectic systems and to be promising for the preparation of granular structures with high magnetoresistance values. Magnetic granular structures have been prepared in Zn(Cd)GeAs2-MnP(As), Zn(Cd)3P(As)2-MnP(As), and (Al,Ga,In)Sb-MnSb systems and the origin of magnetoresistance in these systems is shown to be due to the structure of Mn(CV) ferromagnet clusters.

Growth of magnetic eutectic GaSb-MnSb films by pulsed laser deposition

Eutectic GaSb + MnSb films ranging in thickness from 80 to 130 nm have been grown on sapphire substrates by pulsed laser deposition using mechanical droplet separation. The films were similar in composition to the ablation target, consisting of the eutectic GaSb-MnSb alloy. According to atomic force and electron microscopy data, the films were homogeneous, with p-type conductivity. Their electrical properties depended significantly on deposition conditions. The best films had a resistivity of 7 × 10−3 Ω cm, carrier concentration of 8.1 × 1019 cm−3, and carrier mobility of 102 cm2/(V s). Characteristically, the films had a negative magnetoresistance. Their magnetization curves showed saturation in a magnetic field of ∼1 × 10−1 T. According to the magnetic-field dependences, the coercive force in the films was within 3 × 10−2 T; that is, the films were soft magnets with a small domain size.

Physicochemical foundations of synthesis of new ferromagnets from chalcopyrites AIIBIVC2V

The results of studying phase equilibria of ternary AIIBIVCV systems have been reported. Physicochemical foundations have been developed for the synthesis of new ferromagnets with Curie temperatures above room temperature structurally compatible with basic semiconducting materials. Methods of synthesis and physicochemical properties of manganese-doped AIIBIVC2V ferromagnets have been described. The results of theoretical simulation of magnetic properties have been considered and basic approaches to the explanation of the emergence of ferromagnetism in AIIBIVC2V doped with 3d metals have been surveyed. The most promising ways to produce and study dilute magnetic semiconductors as spintronics materials have been presented.

Synthesis and magnetic properties of the InSb-MnSb eutectic

It has been demonstrated by a combination of physical and chemical methods that InSb and MnSb form an eutectic (6.5 mol % MnSb, Tm = 513°C). A composition consisting of a [110] oriented InSb single crystal matrix and faceted single-crystal MnSb inclusions has been grown by the Bridgman method. The composition shows pronounced electrical conductivity anisotropy. The electrical conductivity along needle-like MnSb inclusions is 5 times higher than the electrical conductivity in the perpendicular direction. The composition possesses magnetic properties and has a Curie temperature of ∼600 K. The material is of interest as a substrate for ferromagnet/semiconductor heterostructures.

Magnetic and electrical properties of Cd3As2 + MnAs composite

A new ferromagnetic material based on a Cd3As2 + MnAs composite with the Curie point of 320 K has been prepared. Magnetic and electrical properties of the composite have been found to be determined by manganese arsenide nanoclusters. The composite has metallic conduction. Its resistance decreases with increasing magnetic field both at low and room temperatures, indicating spin-dependent scattering mechanisms and exchange interactions between magnetic nanoclusters in the composite.

Emergence of pressure-induced metamagnetic-like state in Mn-doped CdGeAs2 chalcopyrite

The effect of hydrostatic pressure on resistivity and magnetic ac susceptibility has been studied in Mn-doped CdGeAs2 room-temperature (RT) ferromagnetic chalcopyrite with two types of MnAs micro-clusters. The slight increase of temperature by about 30 K in the region between RT and Curie temperature TC causes a significant change in the positions of pressure-induced semiconductor-metal transition and magnetic phase transitions in low pressure area. By conducting measurements of the anomalous Hall resistance in the field H ≤ 5 kOe, we present experimental evidence for pressure-induced metamagnetic-like state during the paramagnetic phase at pressure P ≈ 5 GPa.

Magnetic and electrical properties of Zn3P2 + MnP materials

We have synthesized a new ferromagnetic material based on a Zn3P2 + MnP composite with a Curie temperature of 290 K. Experimental data demonstrate that its magnetic and electrical properties are determined by manganese phosphide nanoclusters. The composite has metallic conductivity. Its electrical resistance drops with increasing magnetic field, and its magnetoresistance in a magnetic field of 14 T at 7 K reaches 9%.

Phase equilibria and electrical and magnetic properties of a eutectic in the GaSb-MnSb system

A set of physicochemical analysis methods showed that GaSb and MnSb form a eutectic at 41 mol % MnSb and Tmelt = 632°C. The eutectic is of the platelet type and has metallic conduction. The eutectic GaSb + MnSb is a composite ferromagnetic with a Curie temperature of ∼600 K. The behavior of the electrical resistance in a magnetic field is complex. At low magnetic fields up to 0.8 T, the resistance abruptly drops, and at high magnetic fields, it slowly increases. Such behavior occurs both at low temperatures (5 K) and at 300 K. The change of the trend in the resistance takes place at the magnetic field at which there is magnetization saturation in the magnetic field dependences. Such a dependence of the resistance on the magnetic field is explained by a change of the mechanism of scattering of charge carriers.

Novel ferromagnetic Mn-doped ZnSiAs2 chalcopyrite with Curie point exceeded room temperature

Based on Mn-doped chalcopyrite ZnSiAs2 the new dilute magnetic semiconductor with p-type conductivity was produced. The Curie temperature behavior of the produced semiconductor is distinctly dependent on the Mn concentration: 325 K for 1 wt.% and 337 K for 2 wt.% of Mn, consequently. Magnetization, electrical resistance, magnetic resistance and Hall effect of mentioned compositions were studied. Temperature dependence of magnetization M(T) have complicate behavior. For T  15 K the M(T) dependence is characteristic for superparamagnetic and at T > 15 K magnetization is sum of magnetizations of ensemble of superparamagnetic clusters and ferromagnetic phase contained frustration regions.

Electrical and magnetic properties of the diluted magnetic semiconductors Cd1 − xMnxGeP2 and Cd1 − xMnxGeAs2 at high pressures

The structural and magnetic phase transitions and magnetoresistance of the diluted magnetic semiconductors Cd1 − xMnxGeAs2 and Cd1 − xMnxGeP2 have been studied at high hydrostatic pressures, up to 7 GPa. The normal and anomalous Hall coefficients of the samples have been determined graphically from experimental data.