Oscillating magnetoresistance due to fragile spin structure in metallic GdPd3_3

Studies on the phenomenon of magnetoresistance (MR) have produced intriguing and application-oriented outcomes for decades--colossal MR, giant MR and recently discovered extremely large MR of millions of percents in semimetals can be taken as examples. We report here the investigation of oscillating MR in a cubic intermetallic compound GdPd$_3$, which is the only compound that exhibits MR oscillations between positive and negative values. Our study shows that a very strong correlation between magnetic, electrical and magnetotransport properties is present in this compound. The magnetic structure in GdPd$_3$ is highly fragile since applied magnetic fields of moderate strength significantly alter the spin arrangement within the system--a behavior that manifests itself in the oscillating MR. Intriguing magnetotransport characteristics of GdPd$_3$ are appealing for field-sensitive device applications, especially if the MR oscillation could materialize at higher temperature by manipulating the magnetic interaction through perturbations caused by chemical substitutions.Comment: 10 pages, 7 figures. A slightly modified version is published in Scientific Report

Magnetic and magnetocaloric properties of (Gd1-xYx)(2)NiSi3 compounds (x=0.25, 0.5, 0.75)

In this work, we report the magnetic dilution effect on the magnetic and magnetocaloric properties of (Gd1-xYx)(2)NiSi3 (x = 0.25, 0.5, 0.75) compounds by partial substitution of Y ions in Gd2NiSi3. The X-ray diffraction studies indicate all theses compounds form in AlB2 type hexagonal crystal structure. The dc magnetic measurements reveal the compounds undergo antiferromagnetic like phase transition below 11.5, 7.2, and 3.1 K for x = 0.25, 0.5 and 0.75 compositions, respectively. The magnetic ground state of the compounds becoming increasingly fragile with the increase in Y concentration, and results in magnetic field induced ferromagnetic transition. Such change in magnetic spin configuration is responsible for moderately large magnetic entropy change (Delta S-M (similar to)19.3 J/kg-K, 14.8 J/kg-K and 9.8 J/kg-K for x = 0.25, 0.5, and 0.75, respectively, for Delta H = 7T) in the cryogenic temperature region. The relative cooling power (RCP) has also been estimated for all the compounds that appears to be modest ((similar to)503 J/kg for 7T magnetic field change) for x = 0.25 analogue and reduces further with magnetic dilution effect caused by Y substitution

Attack Graph Generation and Analysis Techniques

As computer networks are emerging in everyday life, network security has become an important issue. Simultaneously, attacks are becoming more sophisticated, making the defense of computer networks increasingly difficult. Attack graph is a modeling tool used in the assessment of security of enterprise networks. Since its introduction a considerable amount of research effort has been spent in the development of theory and practices around the idea of attack graph. This paper presents a consolidated view of major attack graph generation and analysis techniques

Interplay between Co-3d and Ce-4f magnetism in CeCoAsO

We have investigated the ground state properties of polycrystalline CeCoAsO by means of magnetization, specific heat and solid state NMR. Susceptibility and specific-heat measurements suggest a ferromagnetic order at about, $T_\mathrm{C}$=75 K. No further transitions are found down to 2 K. At 6.5 K a complex Schottky type of anomaly shows up in the specific heat results. The interplay between Ce-4f and Co-3d magnetism being responsible for that anomaly is discussed. Furthermore $^{75}$As NMR investigations have been performed to probe the magnetism on a microscopic scale. As-NMR spectra are analysed in terms of first and second order quadrupolar interaction. The anisotropic shift component $K_{\mathrm{ab}}$ and $K_{\mathrm{c}}$ could be derived from the $^{75}$As powder spectra. Towards lower temperature a strong shift anisotropy was found. Nonetheless $K_{\mathrm{iso}}$ tracks the bulk susceptibility down to $T=$50 K very well. Furthermore the presence of weak correlations among the Ce ions in the ferromagnetic state is discussed. The observed increase of $C/T$ towards lower temperatures supports this interpretation.Comment: 6 pages, 4 figures, Accepted in Physical Review

Ferromagnetically correlated clusters in semi-metallic Ru2NbAl Heusler alloy

In this work, we report the structural, magnetic and electrical and thermal transport properties of the Heusler-type alloy Ru2NbAl. From the detailed analysis of magnetization data, we infer the presence of superparamagnetically interacting clusters with a Pauli paramagnetic background, while short-range ferromagnetic interaction is developed among the clusters below 5 K. The presence of this ferromagnetic interaction is confirmed through heat capacity measurements. The relatively small value of electronic contribution to specific heat, gamma (~2.7 mJ/mol-K2), as well as the linear nature of temperature dependence of Seebeck coefficient indicate a semi-metallic ground state with a pseudo-gap that is also supported by our electronic structure calculations. The activated nature of resistivity is reflected in the observed negative temperature coefficient and has its origin in the charge carrier localization due to antisite defects, inferred from magnetic measurements as well as structural analysis. Although the absolute value of thermoelectric figure of merit is rather low (ZT = 5.2*10-3) in Ru2NbAl, it is the largest among all the reported non-doped full Heusler alloys.Comment: 25 pages, 14 figure

Superparamagnetic and metal-like Ru2TiGe: a propitious thermoelectric material

We report a study of structural, magnetic, heat capacity and thermoelectric properties of a Rubased Heusler alloy, Ru2TiGe. The magnetic measurements reveal that at higher temperatures, diamagnetic and Pauli paramagnetic contributions dominate the magnetic behaviour whereas, at lower temperatures (T<= 20 K), superparamagnetic interaction among clusters is observed. Effect of such magnetic defects is also evident in the electrical resistivity behaviour at lower temperatures. Though the temperature dependence of resistivity exhibits a metal-like nature, the large value of Seebeck coefficient leads to an appreciable power factor of the order of 1 mW/mK2 at 300 K. Large power factor as well as low thermal conductivity results in a value of ZT = 0.025 at 390 K for Ru2TiGe that is orders of magnitude higher than that of the other pure Heusler alloys and point towards its high potential for practical thermoelectric applications

Magnetic frustration driven by conduction carrier blocking in Nd2_2Co0.85_{0.85}Si2.88_{2.88}

The intermetallic compound Nd$_2$Co$_{0.85}$Si$_{2.88}$ having a triangular lattice could be synthesized in single-phase only with defect crystal structure. Investigation through different experimental techniques indicate the presence of two magnetic transitions in the system. As verified experimentally and theoretically, the high-temperature transition T$_H$ ~ 140 K is associated with the development of ferromagnetic interaction between itinerant Co moments, whereas the low-temperature transition at T$_L$ ~ 6.5 K is due to the coupling among Nd-4f and Co-3d moments, which is antiferromagnetic in nature. Detailed studies of temperature-dependent dc magnetic susceptibility, field dependence of isothermal magnetization, non-equilibrium dynamical behavior, viz. magnetic relaxation, aging effect, magnetic-memory effect, and temperature dependence of heat capacity, along with density functional theory (DFT) calculations, suggest that the ground state is magnetically frustrated spin-glass in nature, having competing magnetic interactions of equivalent energies. DFT results further reveal that the 3d/5d-conduction carriers are blocked in the system and act as a barrier for the 4f-4f RKKY interactions, resulting in spin-frustration. Presence of vacancy defects in the crystal are also conducive to the spin-frustration. This is an unique mechanism of magnetic frustration, not emphasized so far in any of the ternary R$_2$TX$_3$ (R=rare-earth, T=transition elements and X=Si, Ge, In) type compounds. Due to the competing character of the itinerant 3d and localized 4f moments, the compound exhibits anomalous field dependence of magnetic coercivity.Comment: 16 pages, 15 figure