R. K. Arslanov

Effect of Hydrostatic Pressure on the Transport Properties of Cadmium Diarsenide Crystals

The electrical resistivity and Hall coefficient of n-type CdAs2crystals cut along [001] and [100] were measured at hydrostatic pressures in the range 0–9 GPa. The ρ(P) and RH(P) curves for the [001] direction show three peaks at 1.8, 3, and 5.5 GPa. In the [100] direction, the curves show two peaks at 3 and 5.5 GPa. The peaks at 1.8 and 3 GPa are likely related to impurity levels. The peak at 5.5 GPa is due to the phase transition of CdAs2 . The parameters of the phase transition are determined.

Anomalies of magnetic properties and magnetovolume effect in Cd1−xMnxGeAs2 at hydrostatic pressure

We present the experimental results of the effect hydrostatic pressure up to P ≤ 7 GPa applied at the room temperatures in diluted magnetic semiconductor Cd1−xMnxGeAs2 (x = 0.06 − 0.3). We have found the pressure areas at which anomalies in magnetic properties were observed. Induced by hydrostatic pressure at P > 1.5 GPa magnetic phase transitions, interpreted as metamagnetic transition, were observed. The transitions from magnetic-ordered into magnetic disordered phases in region P > 4.1 GPa on the pressure dependences of relative volume compressibility were detected. We estimated the values of bulk modulus and volume magnetostriction. It is shown that high pressures significantly decrease the Curie temperature with values dTC/dP ≈ (−14.0 ÷ −6.8) K/GPa.

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.

Pressure-induced metamagnetic transition in the Cd0.7Mn0.3GeAs2 ferromagnetic semiconductor

The magnetic susceptibility χ/χ0 and the longitudinal Δρzz/ρ0 and transverse Δρxx/ρ0 magnetoresistances have been measured as functions of the hydrostatic pressure P ≤ 7 GPa at room temperature in the high-temperature ferromagnetic semiconductor Cd0.7Mn0.3GeAs2 with a chalcopyrite structure and the Curie temperature Tc = 355 K. A pressure-induced metamagnetic transition from the low-magnetization state to the high-magnetization state has been observed in Cd0.7Mn0.3GeAs2 near the magnetic ordering temperature. This transition is accompanied by the hysteresis of the magnetic susceptibility and magnetoresistance.

Phase transformation of p-Cd1 − xMnxGeAs2 single crystals at 5.5 GPa

The electrical resistivity and Hall coefficient of oriented single-crystal p-Cd1 − xMnxGeAs2 samples have been measured at high pressures. The results indicate that the crystals undergo a reversible structural transformation at 5.5 GPa, which is independent on the sample orientation.

Transport peculiarities and phase transition in diluted magnetic semiconductors CdGeAs2: mn at high hydrostatic pressure

Pressure dependences of resistivity ρ(P) and Hall coefficient RH have been measured for the novel high-temperature ferromagnetic semiconductor p-Cd1-xMnxGeAs2 (x=0÷0.36) at the room temperature. Structural phase transitions with positions shifting towards low pressures, when percentage of manganese increases from 5.9 GPa for CdGeAs2 to 4.8 GPa for p-Cd0.64Mn0.36GeAs2, are found out. Some anomalies of dependence RH(P), which we attribute to magnetic properties and the presence of impurities, are found out for the crystals with the greater percentage of manganese (x≥0.18).

Resistivity and Hall Coefficient of Zinc Diarsenide at Hydrostatic Pressures of up to 9 GPa

The electrical properties of ZnAs2 single crystals were measured along the [001] direction in the pressure range from 0 to 9 GPa. The electrical resistivity of the crystals was found to decrease by one order of magnitude as the pressure increases from 0 to 7 GPa, without significant changes at higher pressures. The Hall coefficient drops by two orders of magnitude as the pressure increases from 0 to 7 GPa and remains constant in the range from 7 to 9 GPa.

Pressure control of magnetic clusters in strongly inhomogeneous ferromagnetic chalcopyrites

Room-temperature ferromagnetism in Mn-doped chalcopyrites is a desire aspect when applying those materials to spin electronics. However, dominance of high Curie-temperatures due to cluster formation or inhomogeneities limited their consideration. Here we report how an external perturbation such as applied hydrostatic pressure in CdGeP2:Mn induces a two serial magnetic transitions from ferromagnet to non-magnet state at room temperature. This effect is related to the unconventional properties of created MnP magnetic clusters within the host material. Such behavior is also discussed in connection with ab initio density functional calculations, where the structural properties of MnP indicate magnetic transitions as function of pressure as observed experimentally. Our results point out new ways to obtain controlled response of embedded magnetic clusters.

Electrical and thermoelectric properties of ZnO under atmospheric and hydrostatic pressure

Temperature (for T = 77–400 K) and pressure (for P ≤ 8 GPa) dependences of conductivity σ(T,P). Hall coefficient RH(T, P), and Seebeck coefficient Q(T) were studied in single-crystal n-ZnO samples with the impurity concentration Ni = 1017 − 1018 cm−3 and free-electron concentration n = 1013−1017 cm−3. Single crystals were grown by the hydrothermal method. Dependence of the ionization energy of a shallow donor level on the impurity concentration Ed1(Nd) is determined, along with the pressure coefficients for the ionization energy ∂Ed1/∂P and static dielectric constant ∂x/∂P. A deep defect level with the energy Ed2 = 0.3 eV below the bottom of the conduction band is found. The electron effective mass is calculated from the obtained data on the kinetic coefficients RH(T) and Q(T).

Phase transformations of the ferromagnetic semiconductor Cd1−x MnxGeP2 at pressures of up to 5 GPa

The electrical resistivity and Hall coefficient of Cd1−xMnxGeP2 (x=0−0.19) have been measured at 300 K and hydrostatic pressures of up to 5 GPa. The results indicate that CdGeP2 dissociates to CdP2 and Ge at p = 3.2 GPa, while the incorporation of manganese stabilizes the crystal structure of CdGeP2, and Cd0.81Mn0.19GeP2 undergoes a reversible phase transition at p = 3.5 GPa.