We have bombarded graphite samples with protons at low temperatures and fluences to attenuate the large thermal annealing produced during irradiation. The overall optimization of sample handling allowed us find Curie ${T}_{c}\ensuremath{\gtrsim}350\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ used. magnetization versus temperature shows unequivocally a linear dependence, which can be interpreted as due excitations spin waves in two-dimensional Heisenberg model weak uniaxial anisotropy.

Granular superconductivity in powders of small graphite grains (several tens micrometers) is demonstrated after treatment with pure water. The temperature, magnetic field and time dependence the moment treated powder provides evidence for existence superconducting vortices some similarities to high-temperature granular oxides but even at temperatures above 300 K. Room temperature doped or its interfaces appears be possible. Detailed facts importance specialist readers are published as...

Transport properties of a few hundreds nanometers thick (in the graphene plane direction) lamellae highly oriented pyrolytic graphite (HOPG) have been investigated. Current-Voltage characteristics as well temperature dependence voltage at different fixed input currents provide evidence for Josephson-coupled superconducting regions embedded in internal two-dimensional interfaces, reaching zero resistance low enough temperatures. The overall behavior indicates existence with critical...

Measuring with high precision the electrical resistance of highly ordered natural graphite samples from a Brazil mine, we have identified transition at $\sim$350~K $\sim$40~K width. The step-like change in temperature resistance, its magnetic irreversibility and time dependence after field change, consistent trapped flux creep, partial expulsion obtained by magnetization measurements, suggest existence granular superconductivity below 350~K. zero-field virgin state can only be reached again...

We have studied the resistivity of a large number highly oriented graphite samples with areas ranging from several mm$^2$ to few $\mu$m$^2$ and thickness $\sim 10 $nm tens micrometers. The measured resistance can be explained by parallel contribution semiconducting graphene layers low carrier density $< 10^9$ cm$^{-2}$ one metallic-like internal interfaces. results indicate that ideal Bernal stacking structure is narrow-gap semiconductor an energy gap $E_g \sim 40 $meV.

We have studied the change in magnetic properties produced on highly oriented pyrolytic graphite samples by irradiation of H, C, and N ions mega-electron-volt energy range. The use specially made sample holders for measurements provided high reproducibility allowing us to obtain directly effects without any corrections or subtractions. Our results show that three phenomena are triggered defects irradiation, namely, Curie-type paramagnetism, ferromagnetism an anomalous paramagnetic state...

Iridate thin films are a prerequisite for any application utilizing their cooperative effects resulting from the interplay of strong spin-orbit coupling and electronic correlations. Here, heteroepitaxial ${\mathrm{Na}}_{2}{\mathrm{IrO}}_{3}$ with (001) out-of-plane crystalline orientation well-defined in-plane epitaxial relationship presented on various oxide substrates. Resistivity is dominated by three-dimensional variable-range hopping mechanism in large temperature range between 300 K 40...

In this work we investigate the electrical transport properties and growth conditions of tungsten carbon (WC) palladium (PdC) nanostructures on Si substrates using a focused ion beam scanning electron microscope. situ energy dispersive x-ray (EDX) characterizations reveal that electron-beam-induced WC PdC nanostructure depositions (EBID) show lower metal concentration (below 3% atomic percentage) than in ion-beam-induced deposition (IBID) (above 20%). case pattern Pd/C content were optimized...

The electrical, in-plane resistance as a function of temperature $R(T)$ bulk and mesoscopic thin graphite flakes obtained from the same batch was investigated. Samples thicker than $\ensuremath{\sim}30$ nm show metalliclike contribution in range that increases with sample thickness, whereas semiconductinglike behavior observed for thinner samples. dependence all measured samples several others literature can be very well explained between 2 1100 K assuming three contributions parallel:...

High-resolution magnetoresistance data in highly oriented pyrolytic graphite thin samples manifest nonhomogenous superconductivity with critical temperature ${T}_{c}\ensuremath{\sim}25\text{ }\text{K}$ and higher temperature. Our claim is based mainly the observation of anomalous hysteresis loops resistance versus magnetic field that cannot be assigned to irreversibility but indicates existence Josephson-coupled superconducting grains. In addition we observe quantum resonances can Andreev...

We investigate the dependence of electrical resistivity and magnetoresistance single crystalline micrometer-sized graphite samples a few tens nanometers thick on defect concentration produced by irradiation at low fluences. show that carrier density $n$ is extremely sensitive to induced defects for concentrations as $\ensuremath{\sim}0.1\text{ }\text{ppm}$ follows $n\ensuremath{\sim}1/{R}_{V}^{2}$ with ${R}_{V}$ distance between in graphene plane. These Shubnikov-de Haas oscillations results...

In this work we investigated correlations between the internal microstructure and sample size (lateral as well thickness) of mesoscopic, tens nanometer thick graphite (multigraphene) samples temperature $(T)$ field $(B)$ dependence their electrical resistivity $\rho(T,B)$. Low energy transmission electron microscopy reveals that original highly oriented pyrolytic material -- from which multigraphene were obtained by exfoliation is composed a stack $\sim 50 $nm micrometer long crystalline...

In this work we show that the spreading Ohmic resistance of a quasi-two-dimensional system size $\ensuremath{\Omega}$, thickness $t$, and with constriction $W$ connecting two half-parts resistivity $\ensuremath{\rho}$ goes as $(2\ensuremath{\rho}/\ensuremath{\pi}t)\text{ln}(\ensuremath{\Omega}/W)$, diverging logarithmically size. Measurements in highly oriented pyrolytic graphite (HOPG) well numerical simulations confirm relation. Furthermore, present an experimental method allows us to...

The intrinsic values of the carriers mobility and density graphene layers inside graphite, well known structure built on these in Bernal stacking configuration, are not mainly because most research was done rather bulk samples where lattice defects hide their values. By measuring electrical resistance through microfabricated constrictions micrometer small graphite flakes a few tens nanometers thickness we studied ballistic behavior carriers. We found that carriers' mean free path is large...

Abstract Transparent p‐type conductive γ‐CuI thin films typically exhibit unexpectedly high hole mobilities in the range of 10 cm 2 V −1 s even when heavily textured. To explain this phenomenon, transport properties such are investigated. The temperature‐dependent resistivities textured (111)‐oriented with different carrier concentration fitted using fluctuation‐induced tunneling conductivity (FITC) model series a power law. FITC describes barriers at grain boundaries whereas law considers...

Conduction electrons in graphite are expected to have micrometer large de Broglie wavelength as well mean free path. A direct influence of these lengths the electric transport properties finite-size samples was neglected past. We provide a evidence this effect through size dependence magnetoresistance, which decreases with sample even for hundreds micrometers large. Our findings may explain absence magnetoresistance small few graphene layers and ask general revision experimental theoretical...

We investigated the electric transport properties of single TiO2 nanotubes separated from an anodic titania nanotube array. The temperature dependence resistance measured with conventional four point method all samples show a Mott variable range hopping behavior. results obtained two contacts indicate existence potential barrier between Cr/Au and surfaces, which influence is clearly observable at temperatures &amp;lt;150 K. Impedance spectroscopy in frequency 40 Hz to 1 MHz carried out room...

We have investigated exchange bias effects in bilayers composed by the antiferromagnetic o-YMnO$_3$ and ferromagnetic Co thin film means of SQUID magnetometry, magnetoresistance, anisotropic magnetoresistance planar Hall effect. The magnetization magnetotransport properties show pronounced asymmetries field axes hysteresis loops. Both parameters, $H_{E}(T)$ as well shift $M_E(T)$, vanish around N\'eel temperature $T_N \simeq 45$ K. that $M_E(T)$ is also measured a resistance having those...

High-quality lattice-matched LaNiO3/LaMnO3 superlattices with monolayer terrace structure have been grown on both (111)- and (001)-oriented SrTiO3 substrates by pulsed laser deposition. In contrast to the previously reported experiments, a magnetic exchange bias is observed that reproducibly occurs in thin single layers of 5 7 unit cells, respectively. The theoretically explained charge transfer-induced moments at Ni atoms. Furthermore, magnetization data low temperature suggest two phases...

We present a new method to obtain topological insulator Bi2Se3 thin films with centimeter large lateral length. To produce amorphous films, we have used sequential flash-evaporation at room temperature. Transmission electron microscopy has been verify that the prepared samples are in pure state. During annealing, transform into rhombohedral crystalline structure which was confirmed using X-ray diffraction and Raman spectroscopy. Resistance measurements of show expected Mott variable range...