Influence of Bound Magnetic Polarons on Magnetic and Electrical Properties in Metallic n-Cd0.95\text{}_{0.95}Mn0.05\text{}_{0.05}Se

Doping-induced contribution to the millikelvin magnetic susceptibility of Cd$\text{}_{0.95}$Mn$\text{}_{0.05}$Se:In has been found to undergo a maximum at n ≈ 2n$\text{}_{c}$, and to vanish for n ≥ 8n$\text{}_{c}$, where n$\text{}_{c}$ is the electron concentration corresponding to the metal-insulator transition. This confirms the presence, also in the metallic phase, of bound magnetic polarons. Their slow dynamics may account for hysteresis visible in our magnetoresistance data

Search for Dimensional Effects in Spin-Glass Transition in Thin Cd1−x\text{}_{1-x}Mnx\text{}_{x}Te Multilayers

SQUID magnetic measurements of CdTe/Cd$\text{}_{1-x}$Mn$\text{}_{x}$Te, x ≃ 0.5, multi-layers with different CdMnTe layer thickness w reveal the persistence of the spin-glass irreversibilities down to ≃ 16 Å thin layers, i.e., well beyond the previously postulated 40 Å as a quasi-2D threshold. The freezing temperature T$\text{}_{f}$ is found to be a monotonic function of w, and it obeys a scaling law T$\text{}_{f}$ ∝ w$\text{}^{a}$, with a 0.8 similar to that for canonical spin-glasses. Magnetic properties of all studied structures are found to be independent of the orientation of the magnetic field

Search for Dimensionality Crossover of Spin-Glass Freezing in Superlattices of Cd0.50\text{}_{0.50}Mn0.50\text{}_{0.50}Te/CdTe

SQUID measurements of the time decay of the thermoremanent magnetization (field-cooled in 1000 Oe) at long time scale, 10$\text{}^{2}$ 0.05, indicating the absence of the phase transition at nonzero temperature under the experimental conditions

Proceedings of the XI National School "Collective Phenomena and Their Competition

The magnetotransport in the vicinity of the metal-insulator transition in La1.85Sr0.15CuxZn1−xO4 is studied in the mK temperature range. Both longitudinal and transverse magnetoresistance are negative indicating the importance of spin effects. The magnitude of transverse magnetoresistance is larger than the magnitude of longitudinal magnetoresistance, indicating the absence of positive orbital magnetoresistance, in sharp contrast to strongly underdoped La 2−x Sr x CuO 4 . Both transverse and longitudinal magnetoresistance are proportional to the relative change of zero-field conductivity. This suggests that low-temperature localization of carriers may originate in the spin-disorder scattering on the spin droplets around Zn-impurities

Metal-Insulator Transition in Zinc-Doped LaSrCuO

The magnetotransport in the vicinity of the metal-insulator transition in La$\text{}_{1.85}$Sr$\text{}_{0.15}$Cu$\text{}_{x}$Zn$\text{}_{1-x}$O$\text{}_{4}$ is studied in the mK temperature range. Both longitudinal and transverse magnetoresistance are negative indicating the importance of spin effects. The magnitude of transverse magnetoresistance is larger than the magnitude of longitudinal magnetoresistance, indicating the absence of positive orbital magnetoresistance, in sharp contrast to strongly underdoped La$\text{}_{2-x}$Sr$\text{}_{x}$CuO$\text{}_{4}$. Both transverse and longitudinal magnetoresistance are proportional to the relative change of zero-field conductivity. This suggests that low-temperature localization of carriers may originate in the spin-disorder scattering on the spin droplets around Zn-impurities

Conductance Fluctuations in Microstructures of HgCdMnTe Bicrystals

Microscopic four-contact probes to semimagnetic HgCdMnTe grain-boundary inversion layers have been photolithographically patterned. Magnetoresistance measurements performed on these samples revealed aperiodic conductance fluctuations of the magnitude of the order of e$\text{}^{2}$/h. Quantitative analysis of both fluctuation amplitude and their mean period indicate that we have approached the mesoscopic regime in our system. This opens new possibilities in studies of spin-subsystem dynamics in semimagnetic semiconductors

Mesoscopic Phenomena in Microstructures of IV-VI Epilayers

Magnetoresistance measurements of photolithographically patterned PbSe and Pb$\text{}_{1-y}$Mn$\text{}_{x}$Se microstructures were performed. Reproducible magnetoconductance fluctuations with the amplitude increasing with decreasing temperature were observed. Unexpectedly, these fluctuations contain a component periodic in the magnetic field, and their magnitude is greater than that expected from the current theory of the universal conductance fluctuations. Possible explanations are discussed

Conductance Fluctuations in Quantum Wires of n-CdTe and n-Cd1−x\text{}_{1-x}Mnx\text{}_{x}Te

We present millikelvin studies of magnetoconductance in submicron wires of In-doped n$\text{}^{+}$-CdTe and n$\text{}^{+}$-Cd$\text{}_{0.99}$Mn$\text{}_{0.01}$Te epilayers. Weak-field magnetoresistance which arises from quantum localization as well as universal conductance fluctuations have been observed. The exchange coupling to magnetic impurities is shown to decrease the correlation field of the fluctuations. This novel effect is interpreted by invoking a new driving mechanism of the magnetoconductance fluctuations - the redistribution of the electrons between energy levels of the system, induced by the giant s-d spin-splitting of the electronic states