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Currently, complex ferromagnetic semiconductor systems are of significant interest due to their potential applicability in spintronics. A key feature in order to use semiconductor materials in spintronics is the presence of room temperature ferromagnetism. This feature was recently observed and is intensively studied in several Mn-alloyed II-IV-V2 group diluted magnetic semiconductor systems. The paper reviews the origin of room temperature ferromagnetism in II-IV-V2 compounds. In view of our recent reports the room temperature ferromagnetism in Mn-alloyed chalcopyrite semiconductors with more than 5 molar % of Mn is due to the presence of MnAs clusters. The solubility of magnetic impurities in bulk II-IV-V2 materials is of the order of a few percent, depending on the alloy composition. High values of the conducting hole - Mn ion exchange constant Jpd have significant value equal to 0.75 eV for Zn0.997Mn0.003GeAs2. The sample quality has significant effect on the magnetotransport of the alloy. The magnetoresistance of the alloy change main physical mechanism from spin-disorder scattering and weak localization for homogeneous samples to cluster-related geometrical effect observed for nanocomposite samples. The magnetoresistance of the II-IV-V2 alloys can be then tuned up to a few hundreds of percent via changes of the chemical composition of the alloy as well as a degree of disorder present in a material. [Projekat Ministarstva nauke Republike Srbije, br. III45003]

Magnetic and transport properties of [Zn.sub.1-x][Mn.sub.x]Ge[As.sub.2] semimagnetic semiconductor with the varying the chemical composition are studied. The high field magnetoresistance has displayed the presence of giant magnetoresistance effect with maximum amplitudes around 50% because of the presence of nanosize ferromagnetic grains. .

The vacancy defects in chalcopyrite semimagnetic semiconducting mixed [Zn.sub.1-x][(Mn,CO).sub.x]Ge[As.sub.2] bulk crystals are studies by using positron annihilation spectroscopy. The results have shown that the p-type conductivity in the samples is not because of cation vacancy related acceptor centers

In CdGeAs2, a metamagnetic phase transition and a negative magnetic resistance induced by high pressure were found and studied. [ABSTRACT FROM AUTHOR]

• Mn-doped Cd 3 As 2 crystals were obtained from elemental and binary precursors. • Mn doping promotes structural transition into secondary polymorph modification. • At lower Mn content ternary Cd 3−x Mn x As 2 compound is formed. • Above solubility limit (x ~0.13) the MnAs phase was detected. • The formation of CdAs 2 phase in Cd 3−x Mn x As 2 + MnAs composites is suppressed. [Display omitted] We studied the effect of Mn on the structure and properties of Cd 3−x Mn x As 2 crystals with x = 0–0.24, synthesized by direct fusion of high-purity elements. Obtained X-ray diffraction patters suggest that the incorporation of Mn promotes a structural phase transition from primary α-Cd 3 As 2 (x = 0) phase to the α''– Cd 3 As 2 (x = 0.24) phase, while at intermediate compositions both phases can coexist. In addition, the increase of Mn content results in the decrease of lattice cell parameters, which effectively saturates for x > 0.13. Microstructural, calorimetric and magnetometry studies suggest that at high Mn content (x = 0.24) secondary MnAs phase appears. Using obtained results, we estimated the solubility limit of Mn in Cd 3 As 2 as x ~0.13, which corresponds to the formation of ternary Cd 3−x Mn x As 2 compound where Cd atoms are partially substituted by Mn. Formation of ternary compound was also suggested by the results for Cd 3 As 2 + MnAs composite systems, where we also observed the presence of CdAs 2 phase, which is a byproduct of corresponding reaction. Additional studies suggested that the CdAs 2 phase formation in composite system can be prevented if one uses the Cd 3−x Mn x As 2 compound instead of pure Cd 3 As 2 as a matrix material. [ABSTRACT FROM AUTHOR]

Electrical resistivity and Hall coefficient in the samples of Cd1-xMnxGeP2, where x=0/ 0.19, have been measured under hydrostatic pressures up to 5 GPa. All measurements were carried out at T=300 K. A dissociation of Cd1-xMnxGeP2 solid solution was observed and the formation of separated phases of CdP2 and Ge were found at P=3.2 GPa for the Mn fraction x<0.19. The further increase of Mn fraction stabilized a crystal structure and for the compound of Cd0.81Mn0.19GeP2 a reversible phase transition was observed at P=3.5 GPa. [ABSTRACT FROM AUTHOR]

Pressure-dependent resistivity and Hall effect measurements indicate thatp- type Cd1 - xMnx GeAs2 solid solutions withx= 0.06 and 0.18 undergo a high-pressure semiconductor-metal transition. The characteristic points of the phase transition are located, and its dynamics is analyzed in terms of the theory of mixed-phase systems. [ABSTRACT FROM AUTHOR]

The initial stages of the formation of CdAs2-ZnAs2 solid solutions are analyzed in terms of crystalchemical energetics. Given that the bond enthalpies decrease in the orderH(Zn-As)2-based solid solutions are substitutional and ZnAs2-based solid solutions are interstitial, and that the thermochemical stability of the substitutional solid solutions is higher than that of CdAs2 . The conclusions drawn from crystal-chemical analysis correlate with the reported x-ray diffraction, chemical analysis, resistivity, and Hall data for the solid solutions. [ABSTRACT FROM AUTHOR]

The electrical resistance and thermoelectric power ofp-ZnAs2 are measured in the pressure range 15-50 GPa. The results attest to phase transitions at 7-10 and 25-30 GPa. [ABSTRACT FROM AUTHOR]