The conditions in which images are obtained to perform multispectral detection of landmines have a direct influence on the methods that are used to perform automatic detection of landmines. In this paper, two methodologies are proposed: one using traditional classifiers and the other using deep learning, namely, a convolutional neuronal network (CNN). In the first methodology, classifier fusion techniques are also used. The performance of the first methodology was evaluated as a function of the number of landmine features, the environment, and the depth of the mine. In deep learning, a study was carried out based on the feature map, the type of landmine, and the environment. A quantitative analysis shows that traditional classifiers achieved an overall accuracy of above 97% in indoor and outdoor environments for the detection of landmines. The adopted deep learning methodology presented an increase in the performance for larger mines and a decrease for smaller ones. These experimental results shed light on the factors that influence the detection of mines and into the advantages and disadvantages of CNN compared with the classical classifier methods.

Magnetic cobalt nitrides were synthesized via nitriding of cobalt particles under NH3 flux by a multi-step process that includes annealing at two temperatures: 823 K and 623 K. The phases Co4+xN and Co3N1+y were produced and their structure and magnetic properties were studied. Both phases are found to be ferromagnetic with saturation magnetization of 143 A m(2) kg(-1) and 33 A m(2) kg(-1) respectively and decompose above 650 K, before attaining the Curie temperature. Self-consistent Density Functional Theory (DFT) calculations were performed to understand the nitrides structure and magnetic behavior dependence on stoichiometry. The results indicate that the magnetic behavior of the hexagonal nitride is strongly dependent on the nitrogen content. The comparison of the experimental lattice parameters and magnetization values with the DFT calculations allows to determine the stoichiometry of the prepared compounds. (C) 2014 Elsevier B.V. All rights reserved.

The magnetic properties of Mn, Co, and Ni substituted Fe4N are calculated from first principles theory. It is found that the generalized gradient approximation reproduces with good accuracy the magnetic moment and equilibrium volume for the parent Fe4N structure, with the atomic moment largest for the Fe atom furthest away from the N atom (Fe I site), approaching a value of 3 mu(B)/atom, whereas the Fe atom closer to the N atom (Fe II site) has a moment closer to that of bcc Fe. The substitution of Fe for Mn, Co, or Ni, shows an intricate behavior in which the Mn substitution clearly favors the Fe II site, Ni favors substitution on the Fe I site, and Co shows no strong preference for either lattice site. The Ni and Co substitution results in a ferromagnetic coupling to the Fe atoms, whereas Mn couples antiferromagnetically on the Fe II site and ferromagnetically on the Fe I site. For all types of doping, the total magnetic moment is enhanced compared to Fe4N only in the energetically very unfavorable case of Mn doping at the Fe I site.

Although barium ferrate is known to accommodate a range of oxygen stoichiometries, which give rise to distinct magnetic properties, the mechanism underlying this coupling is not clearly understood. In order to address this issue, the electronic and magnetic properties of pseudocubic BaFeO3−δ with 0 ≤δ≤ 0.5 were studied using density functional theory. The present results attest the influence of the oxygen content on the magnetic order: for high oxygen content, the magnetic interactions are predominantly ferromagnetic whereas for oxygen deficient stoichiometries the antiferromagnetic interactions prevail. The threshold separating the two regimes is determined by the competition between double-exchange and super-exchange interactions which sensitively depend on the occupation of the oxygen band. Due to the high electronic affinity of the Fe ions in this compound, which results in a negative ligand to metal charge transfer energy, the system behaves as self-doped and the oxygen content has little effect on the 3d Fe band occupation, affecting instead the occupation of the anionic band.

Abstraet-We consider the macroscopic and microscopic theory of the Magneto-Optical Kerr Effect. It is shown that the Kerr effect is zero without both spin-splitting and spin-orbit coupling. The origin of peaks in the Kerr signal is discussed. For the transition metals Fe, Co and Ni these peaks arise from interband transitions. Results for the fee and hcp forms of Cobalt are presented and compared. Fair agreement with recent experiments is found. The effect of the lattice para.meter and the Drude term on fce Co is also shown.

In this paper we present a comparative analysis of the isostructural compounds MFe4Al8, with M = Y and U. These compounds have different magnetic ground state structures: a cycloid spin spiral in the case of YFe4Al8 and a canted structure in the case of the actinide compound. Model calculations show that it is the presence of a strong spin–orbit coupling in the actinide compound that leads to a magnetic configuration with symmetry properties that differ from the YFe4Al8 cycloid structure. Furthermore we show that in the absence of spin–orbit coupling, the U compound would have the same spin spiral as the Y compound. A further analysis for two actinide compounds, UFe4Al8 and NpFe4Al8, point to similar magnetic ground state structures; however the actinides play different roles in the magnetisms of the two compounds. Despite their differences, all three magnetic structures can be seen as deviations from the type G antiferromagnetic structure. New calculations for UFe4Al8 permit a clarification of previous computational studies, and we present, within a simplified model, an analysis of the Fe–Fe exchange interactions for YFe4Al8 and UFe4Al8, calculated within the frozen magnon approximation.

The present work reports ab-initio density functional theory calculations for the Ruddlesden-Popper phase CaO(CaMnO3)(n) compounds. In order to study the evolution of the properties with the number of perovskite layers, a detailed analysis of the densities of states calculated for each compound and for several magnetic configurations was performed. The effect of distortions of the crystal structure on the magnetic ground state is also analysed and the exchange constants and transition temperatures are calculated for the three compounds using a mean field model. The calculated magnetic ground state structures and magnetic moments are in good agreement with experimental results and previous calculations.

A study of the magnetic structure of YFe4Al8 is presented, based on the reported magnetic structure, as given by a neutron diffraction study; cycloid, with moments in the a–b plane and with two Fe sublattices with a 140° phase difference between them. Calculations were performed, using density functional theory, for cycloids with , with τ varying between 0 and 1. The calculated magnetic structure agrees with the structure deduced from neutron diffraction results, however with a simpler description. The YFe4Al8 magnetic structure can be described by a single Fe lattice with a cycloid propagation vector with τ = 0.865; there is no need for a second Fe lattice with an arbitrary phase difference. We show that the same description can be applied to DyFe4Al8 and HoFe4Al8.

The compound NpFe4Al8 was prepared by direct arc melting of the constituent elements, followed by annealing. It crystallizes in the ThMn12-type structure (space group 14/mmm, a = 8.7480(5) Angstrom, c = 5.0372(4) Angstrom), with the iron atoms completely and only occupying the 8f positions. Magnetization measurements (T = 2-300 K, B = 0-7 T) show a ferrornagnetic-type transition at T-c = 135(2) K and a second anomaly at 118(3) K. The low temperature magnetization cycle is characterized by a hysteresis with a step similar to that previously observed for UFe4Al8 single crystals. First-principles density functional theory calculations of the NpFe4Al8 band structure point to a magnetic structure similar to that of UFe4Al8, in agreement with the observed magnetization cycle. The calculations indicate that the neptunium moment is aligned along one of the a or b axes, and the iron moments form a noncollinear structure in the a-b plane, with the anti ferromagnetic and ferromagnetic contributions perpendicular and antiparallel to the neptunium spin moment, respectively.

The compounds of the U2T2In series, with T=Pt, Pd, Ni have similar crystallographic structures and electronic configurations but different magnetic structures. With DFT band structure calculations we were able to predict the correct ground state structure. Calculated moments are in good agreement with previous neutron diffraction data, comparison of the three compounds allows a better understanding of the origin of the different properties of the compounds: magnetic ordering for U2Ni2In and U2Pd2In and Jahn–Teller effect for U2Pt2In.

In this paper we present the result of the combination of band structure calculations and Monte Carlo simulations. Our results are obtained from a series of Monte Carlo (MC) simulations for YFe2 and GdFe2, based upon the correct lattice structure and using realistic exchange parameters deduced from ab initio calculations and theory. The long-range (itinerant) Fe–Fe interactions are included up to the eighth neighbour shell, whereas the Fe–RE interaction is only considered between the nearest-neighbour sites. Results are in fair agreement with experiment.

The UFexAl12-x series was the object of a systematic experimental study in single crystals with different compositions [Phys. Rev. B 60, 9494 (1999)]. Several experimental technics were used to suggest a magnetic phase diagram of the system. Three different ranges of composition were found to have different magnetic behaviour: x < 4 + delta(1), 4 + delta(1) < x < 5 - delta(2), and x > 5 - delta(2). Here delta(1) and delta(2) are small positive numbers. The UFe4Al8 and UFe5Al7 compounds belong to two different regions of the phase diagram. DFT calculations and symmetry analysis for these two compounds [Phys. Rev. B 60, R 6961 (1999); 65, 94413 (2002)] contributed to the understanding of the origin of the complex magnetic behaviour of the series. In order to complete the systematic study of the series we report calculations of magnetic properties for UFe4.5Al7.5. The latter compound belongs to the third and the most interesting region of the phase diagram with two magnetic phase transitions. Based on this ab initio study, we discuss the proposed phase diagram.

We report symmetry analysis and first-principles density-functional-theory (DFT) calculations of the magnetic structure in UFe5Al7. Two results can be considered as most significant. First, we show that the magnetic structure of UFe5Al7 is noncollinear. This is an important modification of the magnetic phase diagram suggested previously. The noncollinearity is a consequence of the interplay between the symmetry of the magnetic crystal and the spin-orbit coupling. Second, we show that the DFT reproduces a drastic difference in the magnetic structure of UFe5Al7 and UFe4Al8 compounds. This difference appears mainly as a result of a strong variation of the angle between the crystallographic b axis and the 8f Fe moments under the influence of the replacement of one of the Al atoms by the Fe atom. The influence of the orbital polarization correction is discussed.

We report self-consistent energy band calculations using the linear muffin-tin orbital method and the local-spin-density approximation to exchange and correlation in density-functional theory for t ...

For pt. I see ibid., vol. 7, p. 9499 (1995). We examine the compounds U(T)Al forming in the ZrNiAl structure where T is a group 6-8 transition metal. From first-principles calculations we find, in agreement with experiment, the transition from paramagnetism to magnetism across the series. The inclusion of spin-orbit coupling and orbital polarization yields fair agreement with measurements for the calculated magnetic moments. Two magnetic states are found for URhAl.

We consider the macroscopic and microscopic theory of the Magneto-Optical Kerr Effect. It is shown that the Kerr effect is zero without both spin-splitting and spin-orbit coupling. The origin of peaks in the Kerr signal is discussed. For the transition metals Fe, Co and Ni these peaks arise from interband transitions. Results for the fcc and hcp forms of Cobalt are presented and compared. Fair agreement with recent experiments is found. The effect of the lattice parameter and the Drude term on fcc Co is also shown.