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The impact of an applied electric field on the exchange coupling parameters has been investigated based on first-principles electronic structure calculations by means of the KKR Green function method. The calculations have been performed for a Fe film, free-standing and deposited on two different substrates, having 1 monolayer (ML) thickness to minimize the effect of screening of the electric field typical for metallic systems. By comparing the results for the free-standing Fe ML with those for Fe on the various substrates, we could analyze the origin of the field-induced change of the exchange interactions. Compared to the free-standing Fe ML, in particular rather pronounced changes have been found for the Fe/Pt(111) system due to the localized electronic states at the Fe/Pt interface, which are strongly affected by the electric field and which play an important role for the Fe-Fe exchange interactions.

We employ first-principles alloy theories to assess the influence of local lattice distortions on the electronic transport of six body-centered cubic high-entropy alloys. We find weak disorder smearing of bands in the ideal lattice due to the similar number of valence electrons among alloying elements. Allowing relaxation, we demonstrate that local distortions in NbMoTaW and VNbMoTaW are small while they are anomalously large in HfNbTiZr, HfNbTaTiZr, VCrZrNb and CrNbTiVZr. The Fermi surfaces of the latter are strongly smeared by local distortions, leading to nearly-saturated resistivities. These findings address the important local relaxation effect on the electronic structure of high-entropy alloys.

Herein we present a study on the interplay of chemical composition with respect to $x$ in antiferromagnetic ${\mathrm{Co}}_{x}\mathrm{Nb}{\mathrm{S}}_{2}$ and the anomalous Hall effect (AHE) in the magnetically ordered state. The AHE diminishes virtually completely in samples with exceeding Co content compared to the idealized composition of $x=1/3$. For stoichiometric samples the effect is weak but shows a sign reversal just below the magnetic ordering temperature. With increasing deficiency, the magnitude of the AHE compared to the ordinary Hall effect increases and additionally an exchange-biaslike effect can be observed. The results reveal the chemical composition of the samples as tuning parameter for the AHE in ${\mathrm{Co}}_{x}\mathrm{Nb}{\mathrm{S}}_{2}$. Accompanying first-principles calculations demonstrate that the electronic band structure is only slightly affected by disorder and deficiency of Co, but an impact on the magnetic exchange coupling can be inferred. The results are interesting for the research on $3d$-metal inserted transition-metal dichalcogenides and in a broader context for the understanding and design of antiferromagnet-based spintronic materials.

Various technical developments extended the potential of angle-resolved photoemission (ARPES) tremendously during the last twenty years. In particular improved momentum, energy and spin resolution as well as the use of photon energies from few eV up to several keV makes ARPES a rather unique tool to investigate the electronic properties of solids and surfaces. With our work we present a generalization of the state of the art description of the photoemission process, the so called one-step model that describes excitation, transport to the surface and escape into the vacuum in a coherent way. In particular, we present a theoretical description of temperature-dependent ARPES with a special emphasis on spin fluctuations. Finite temperature effects are included within the so called alloy analogy model which is based on the coherent potential approximation and this way allows to describe uncorrelated lattice vibrations in combination with spin fluctuations quantitatively on the same level of accuracy. To demonstrate the applicability of our approach a corresponding numerical analysis has been applied to spin- and angle-resolved photoemission of Fe(100) at finite temperatures., Submitted to PRB

The way doping affects the spin wave stiffness and the exchange stiffness of permalloy (Py) is investigated via ab-initio calculations, using the Korringa-Kohn-Rostoker (KKR) Green function formalism. By considering various types of dopants of different nature (V, Gd, and Pt), we are able to draw general conclusions. To describe the trends of the stiffness with doping is it sufficient to account for the exchange coupling between nearest neighbors. The polarizability of the impurities is not an important factor for the spin wave stiffness. Rather, the decisive factor is the hybridization between the impurity and the host states as reflected by changes in the Bloch spectral function. Our theoretical results agree well with earlier experiments., 8 figures, 5 tables

The ab initio Korringa-Kohn-Rostoker method combined with the coherent potential approximation (CPA) was employed to investigate the electronic, magnetic, and transport properties of medium-entropy face-centered-cubic (fcc) NiCoMn solid solution alloys. By comparing the CPA electronic structure with that from supercell calculations, we uncovered an unconventional CPA ground state, which correctly distinguishes two equally populated Mn CPA components---with large spin moments but opposite orientations. Using the spin spiral calculations, we further demonstrated that this ground state is most energetically favorable in the presence of spin noncollinearity, and no significant longitudinal spin fluctuation is observed, justifying the applicability of the Heisenberg model. The finite-temperature magnetism was further studied using different approximations based on the Heisenberg model, and we found the Mn moments to be fully disordered at low temperature due to a small net effective Weiss field on Mn. In addition, the magnetic effect on the electron scattering at finite temperatures was evaluated and compared with other scattering mechanisms. Since the magnetization-induced electron scattering is almost saturated in the ground state, (full) spin disorder only yields a small addition to the resistivity, whereas the thermal displacements increase it modestly. Finally, we elucidate the role of hydrostatic pressure on the magnetic and transport properties. These findings reflect the importance of the magnetic signatures on the physical properties of alloys, and they provide a window into magnetism-controlled electronic structure and energy dissipation.

The composition-dependent behavior of the Dzyaloshinskii--Moriya interaction (DMI), the spin-orbit torque (SOT), as well as anomalous and spin Hall conductivities of ${\mathrm{Mn}}_{1\ensuremath{-}x}{\mathrm{Fe}}_{x}\mathrm{Ge}$ alloys have been investigated by first-principles calculations using the relativistic multiple scattering Korringa--Kohn--Rostoker (KKR) formalism. The ${D}_{\mathrm{xx}}$ component of the DMI exhibits a strong dependence on the Fe concentration, changing sign at $x\ensuremath{\approx}0.85$ in line with previous theoretical calculations as well as with experimental results demonstrating the change of spin helicity at $x\ensuremath{\approx}0.8$. A corresponding behavior with a sign change at $x\ensuremath{\approx}0.5$ is predicted also for the Fermi-sea contribution to the SOT, because this is closely related to the DMI. In the case of anomalous and spin Hall effects it is shown that the calculated Fermi-sea contributions are rather small and the composition-dependent behavior of these effects are determined mainly by the electronic states at the Fermi level. The spin-orbit-induced scattering mechanisms responsible for both these effects suggest a common origin of the minimum of the anomalous Hall effect and the sign change of the spin Hall effect conductivities.

Heusler compounds and alloys form a unique class of intermetallic systems with functional properties interfering with basic questions of fundamental aspects of materials science. Among the functional properties, the magnetic shape memory behavior (Planes et al., J Phys: Condens Matter 21:233201 (29 pp), 2009) and the ferrocaloric effects like the inverse magnetocaloric effect which is associated with the first order magnetostructural transformation with a jump-like change of the magnetization with lowering of temperature (Acet et al., Magnetic-field-induced effects in martensitic Heusler-based magnetic shape memory alloys. In: Bushow KHJ (ed) Handbook of magnetic materials, vol 19. North-Holland, Amsterdam, pp 231–289, 2011) have been intensively investigated in various reviews. Important references can be found in Acet et al. (Magnetic-field-induced effects in martensitc Heusler-based magnetic shape memory alloys. In: Bushow KHJ (ed) Handbook of magnetic materials, vol 19. North-Holland, Amsterdam, pp 231–289, 2011). Besides magnetocaloric effects, other ferroic cooling mechanisms of Heuslers (electrocaloric, barocaloric, and elastocaloric ones) have recently been discussed by Xavier Moya et al. (Nat Mater 13:439–450, 2014). A discussion of caloric effects in ferroic materials including a brief discussion of the importance of correlating time and length scales can be found in Fahler et al. (Adv Eng Mater 14:10–19, 2012). In the present article, we emphasize this item further by showing that, in particular, the physics at different time scales leads to markedly different properties of the Heusler materials. “Rapidly quenched” alloys behave differently from “less rapidly quenched” alloys. In the latter case, the so-called magnetostructural transformation may vanish altogether because of segregation of the alloys into the stoichiometric L21 Heusler phase and L10 Ni-Mn occurs. We argue that this tendency for segregation is at the origin of glassiness in Heuslers.

We represent an approach to calculate micromagnetic model parameters such as the tensor of exchange stiffness, Dzyaloshinskii-Moriya interaction (DMI), as well as spin-wave stiffness. The scheme is based on the fully relativistic Korringa-Kohn-Rostoker Green function (KKR-GF) technique and can be seen as a relativistic extension of the work of Lichtenstein et al. [J. Magn. Magn. Mater. 67, 65 (1987)]. The expression for Dzα elements of DMI differ from the expressions for Dxα and Dyα elements as the former are derived via second-order perturbation term of the energy caused by spin-spiral while the latter are associated with the first-order term. Corresponding numerical results are compared with those obtained using other schemes reported in the literature.

The modification of the magnetization dissipation or Gilbert damping caused by an inhomogeneous magnetic structure and expressed in terms of a wave vector dependent tensor $\underline{\alpha}(\vec{q})$ is investigated by means of linear response theory. A corresponding expression for $\underline{\alpha}(\vec{q})$ in terms of the electronic Green function has been developed giving in particular the leading contributions to the Gilbert damping linear and quadratic in $q$. Numerical results for realistic systems are presented that have been obtained by implementing the scheme within the framework of the fully relativistic KKR (Korringa-Kohn-Rostoker) band structure method. Using the multilayered system (Cu/Fe$_{1-x}$Co$_x$/Pt)$_n$ as an example for systems without inversion symmetry we demonstrate the occurrence of non-vanishing linear contributions. For the alloy system bcc Fe$_{1-x}$Co$_x$ having inversion symmetry, on the other hand, only the quadratic contribution is non-zero. As it is shown, this quadratic contribution does not vanish even if the spin-orbit coupling is suppressed, i.e.\ it is a direct consequence of the non-collinear spin configuration., Comment: 2 figures

The magnetic properties of materials based on two-dimensional transition-metal dichalcogenides (TMDC), namely bulk Fe1/4TaS2 compound as well as TMDC monolayers with deposited Fe films, have been investigated by means of first-principles DFT calculations. Changing the structure and the composition of these two-dimensional systems resulted in considerable variations of their physical properties. For the considered systems the Dzyaloshinskii-Moriya (DM) interaction has been determined and used for the subsequent investigation of their magnetic structure using Monte Carlo simulations. Rather strong DM interactions as well as large vertical bar D-01 vertical bar/J(01) ratios have been obtained in some of these materials, which can lead to the formation of skyrmionic structures varying with the strength of the applied external magnetic field. (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Unusual physical properties like large magnetoresistance (MR) and superconductivity occurring in semimetals with Dirac or Weyl points are often linked to their topologically nontrivial band structures. However, there is an increasing number of reports on semimetals that show large MR in the absence of Dirac or Weyl points. Herein we report an experimental and theoretical study on the layered transition-metal dichalcogenide (TMDC) $\mathrm{HfT}{\mathrm{e}}_{2}$ that shows a large MR of $1350%$ at $T=2$ K and ${\ensuremath{\mu}}_{0}H=9\phantom{\rule{0.16em}{0ex}}\mathrm{T}$ in the absence of Dirac or Weyl points. Moreover, the structure and electrical resistivity under pressure reveal a unique structural transition. These results clearly distinguish $\mathrm{HfT}{\mathrm{e}}_{2}$ from TMDCs like $\mathrm{MoT}{\mathrm{e}}_{2}$ or $\mathrm{WT}{\mathrm{e}}_{2}$ which both exhibit larger MR and are viewed as Weyl semimetals. $\mathrm{HfT}{\mathrm{e}}_{2}$ is an appealing platform for future investigations on the interplay of particular band-structure features and their connection to emerging physical properties.

The finite-temperature transport properties of FeRh compounds are investigated by first-principles density-functional-theory-based calculations. The focus is on the behavior of the longitudinal resistivity with rising temperature, which exhibits an abrupt decrease at the metamagnetic transition point, T = T-m, between ferro-and antiferromagnetic phases. A detailed electronic structure investigation for T >= 0 K explains this feature and demonstrates the important role of (i) the difference of the electronic structure at the Fermi level between the two magnetically ordered states and (ii) the different degree of thermally induced magnetic disorder in the vicinity of T-m, giving different contributions to the resistivity. To support these conclusions, we also describe the temperature dependence of the spin-orbit-induced anomalous Hall resistivity and Gilbert damping parameter. For the various response quantities considered, the impact of thermal lattice vibrations and spin fluctuations on their temperature dependence is investigated in detail. Comparison with corresponding experimental data shows, in general, very good agreement.

The electronic structure and magnetic properties of the $2H\ensuremath{-}{\mathrm{NbS}}_{2}$ compound intercalated by Cr, Mn, and Fe, respectively, have been investigated by means of the Korringa-Kohn-Rostoker method. Magnetic torque calculations result in an easy plane magnetocrystalline anisotropy (MCA) of ${\mathrm{Cr}}_{1/3}{\mathrm{NbS}}_{2}$ for the ground state ($T=0$ K). Relativistic disorder local moment calculations show that the corresponding anisotropy constant decreases monotonously with rising temperature in line with experiment. Going from the Cr and Mn to the Fe intercalated system, the modification of the electronic structure results in a change of the easy axis from in-plane to out-of-plane. It is shown that for ${\mathrm{Cr}}_{1/3}{\mathrm{NbS}}_{2}$ and ${\mathrm{Mn}}_{1/3}{\mathrm{NbS}}_{2}$, the in-plane MCA and Dzyaloshinskii-Moriya interactions give rise to a helimagnetic structure along the hexagonal $c$ axis, following the experimental observations. The negative exchange interactions in the ${\mathrm{Fe}}_{1/3}{\mathrm{NbS}}_{2}$ compound result in a noncollinear frustrated magnetic structure if the MCA is not taken into account. It is shown, however, that a strong MCA along the hexagonal $c$ axis leads to a magnetic ordering referred to as an ordering of the third kind, which was observed experimentally.

Finite temperature effects have a pronounced impact on the transport properties of solids. In magnetic systems, besides the scattering of conduction electrons by impurities and phonons, an additional scattering source coming from the magnetic degrees of freedom must be taken into account. A first-principle scheme which treats all these scattering effects on equal footing was recently suggested within the framework of the multiple scattering formalism. Employing the alloy analogy model treated by means of the CPA, thermal lattice vibrations and spin fluctuations are effectively taken into account. In the present work the temperature dependence of the longitudinal resistivity and the anomalous Hall effect in the strongly correlated metal Gd is considered. The comparison with experiments demonstrates that the proposed numerical scheme does provide an adequate description of the electronic transport at finite temperatures., 7 pages, 6 figures

Physical review / B covering condensed matter and materials physics 93(20), 201110(2016). doi:10.1103/PhysRevB.93.201110, Magnetic properties of NiO have been studied in the multimegabar pressure range by nuclear forward scattering of synchrotron radiation using the 67.4 keV Mössbauer transition of $^{61}$Ni. The observed magnetic hyperfine splitting confirms the antiferromagnetic state of NiO up to 280 GPa, the highest pressure where magnetism has been observed so far, in any material. Remarkably, the hyperfine field increases from 8.47 T at ambient pressure to ∼ 24 T at the highest pressure, ruling out the possibility of a magnetic collapse. A joint x-ray diffraction and extended x-ray-absorption fine structure investigation reveals that NiO remains in a distorted sodium chloride structure in the entire studied pressure range. Ab initio calculations support the experimental observations, and further indicate a complete absence of Mott transition in NiO up to at least 280 GPa., Published by Inst., Woodbury, NY

Temperature-dependent magnetic experiments like pump-probe measurements generated by a pulsed laser have become a crucial technique for switching the magnetization in the picosecond time scale. Apart from having practical implications on the magnetic storage technology, the research field of ultrafast magnetization poses also fundamental physical questions. To correctly describe the time evolution of the atomic magnetic moments under the influence of a temperature-dependent laser pulse, it remains crucial to know if the magnetic material under investigation has magnetic excitation spectrum that is more or less dependent on the magnetic configuration, e.g. as reflected by the temperature dependence of the exchange interactions. In this article, we demonstrate from first-principles theory that the magnetic excitation spectra in Co with fcc, bcc and hcp structures are nearly identical in a wide range of non-collinear magnetic configurations. This is a curious result of a balance between the size of the magnetic moments and the strength of the Heisenberg exchange interactions, that in themselves vary with configuration, but put together in an effective spin Hamiltonian results in a configuration independent effective model. We have used such a Hamiltonian, together with ab-initio calculated damping parameters, to investigate the magnon dispersion relationship as well as the ultrafast magnetisation dynamics of Co and Co-rich CoMn alloys.

We discuss the compositional trends in the electronic structure of Fe–Pd alloys in the composition range relevant for martensitic transformations and magnetic shape-memory applications. The results are obtained within the framework of density functional theory based on the Korringa–Kohn–Rostoker Green's function approach in combination with the coherent potential approximation for the description of disorder. For the body centered cubic structure, we observe with increasing Pd content the gradual disappearance of the pseudogap like structure in the center of the minority spin d -band, while on the face centered cubic side a small peak passes the Fermi level around 80 at. % Fe, which has been related previously to a band-Jahn–Teller instability. In addition, we investigate the structural variation of magnetic properties of the magnetic shape-memory composition Fe 70 Pd 30 based on magnetic exchange parameters obtained from our ab initio calculations being mapped onto a classical Heisenberg model. This allows us to estimate the magnetic transition temperature within a mean field approach and Monte Carlo simulations taking into account the induced nature of the Pd atoms, leading to a close, semi-quantitative agreement with experiment in the latter case.

The electronic properties of the system PdH x have been calculated by means of the self-consistent relativistic KKR-CPA (Korringa–Kohn–Rostoker Coherent Potential Approximation) method of band structure calculations for disordered systems. Using a linear response formalism, the magnetic susceptibility and Knight shift of PdH x have been investigated thoroughly. The corresponding results are discussed in detail in comparison with experimental data. In particular, it is shown that for low H concentrations the H Knight shift is determined by a transferred negative contribution due to the high partial spin susceptibility of Pd.

We present results of an experimental study of magnetic properties of small Ru clusters deposited on a thin Fe film grown on Cu(001) surface. X-ray magnetic circular dichroism (XMCD) measurements show finite spin and orbital moments of Ru dimers and trimers, however a magnetic moment for a Ru monomer has been not observed. A corresponding theoretical study based on the fully relativistic multiple scattering KKR method is presented. Detailed theoretical analysis has been performed to explain the experimental findings. In particular a direct comparison of the calculated XMCD with the experiments suggests diffusion into the surface as a possible reason for the apparent quenching of the spin magnetic moment for Ru monomers.

The title compounds were prepared by reaction of Tl2Q (Q = S, Se and Te) Sc and Q in the temperature range of 200 to 500 °C. The structures of the selenide and the telluride adopt the α-NaFeO2 type, while TlScS2 crystallizes in the β-RbScO2 type structure. The space group is for TlScSe2 and TlScTe2 with a = 3.9370(4) A, c = 23.194(5) A, and a = 4.2129(4) A, c = 24.099(3) A, respectively. The sulphide crystallizes in P63/mmc with a = 3.761(3) A and c = 14.942(4) A. The crystal chemical relations between the three chalcogenides are discussed. According to the electrical measurements and the band structure calculations, the compounds are semiconductors or poor metals.

The possibility of using X-ray Compton scattering to reveal antisymmetric components of the electron momentum density, as a fingerprint of magnetoelectric sample properties, is investigated experimentally and theoretically by studying the polar ferromagnet GaFeO3., This paper discusses the possibility of using Compton scattering – an inelastic X-ray scattering process that yields a projection of the electron momentum density – to probe magnetoelectrical properties. It is shown that an antisymmetric component of the momentum density is a unique fingerprint of such time- and parity-odd physics. It is argued that polar ferromagnets are ideal candidates to demonstrate this phenomenon and the first experimental results are shown, on a single-domain crystal of GaFeO3. The measured antisymmetric Compton profile is very small (≃ 10−5 of the symmetric part) and of the same order of magnitude as the statistical errors. Relativistic first-principles simulations of the antisymmetric Compton profile are presented and it is shown that, while the effect is indeed predicted by theory, and scales with the size of the valence spin–orbit interaction, its magnitude is significantly overestimated. The paper outlines some important constraints on the properties of the antisymmetric Compton profile arising from the underlying crystallographic symmetry of the sample.

The electronic, magnetic, and transport properties of Fe-intercalated $2H\text{\ensuremath{-}}{\mathrm{TaS}}_{2}$ have been investigated by means of the Korringa-Kohn-Rostoker (KKR) method. The nonstoichiometry and disorder in the system have been accounted for using the coherent potential approximation (CPA) alloy theory. A pronounced influence of disorder on the spin magnetic moment has been found for the ferromagnetically ordered material. The same applies for the spin-orbit-induced orbital magnetic moment and magnetocrystalline anisotropy energy. The temperature dependence of the resistivity of disordered $2H{\mathrm{Fe}}_{0.28}{\mathrm{TaS}}_{2}$ investigated on the basis of the Kubo-St\ifmmode \check{r}\else \v{r}\fi{}eda formalism in combination with the alloy analogy model has been found in very satisfying agreement with experimental data. This also holds for the temperature-dependent anomalous Hall resistivity ${\ensuremath{\rho}}_{\mathrm{xy}}(T)$. The role of thermally induced lattice vibrations and spin fluctuations for the transport properties is discussed in detail.

The structural and magnetic properties of Cr 1+ x (Se 1− y Te y ) 2 having a NiAs structure has been studied for (1+ x )=1.27, 1.32 and 1.36 and y =0.75 by means of the Korringa–Kohn–Rostoker (KKR) band structure method. The sub-stoichiometry and the disorder on the chalcogenide sub-lattice has been treated by means of the coherent potential approximation (CPA) alloy theory. From total energy calculations a preferential site occupation on the Cr sub-lattice was found together with an antiparallel alignment of the magnetic moments on the two inequivalent Cr layers. The magnetic properties at finite temperature has been studied by means of Monte Carlo simulations on the basis of a classical Heisenberg Hamiltonian and the exchange coupling parameters calculated from first principles. This approach allowed to determine the critical temperature in good agreement with experiment.

The fully relativistic KKR method has been applied within the framework of spin density functional theory (SDFT) to calculate the electronic and magnetic properties of Co clusters deposited on a Pt(111) and a Au(111) surface, respectively. The influence of spin–orbit coupling on the formation and orientation of the magnetic moments, the central issue of our investigations, was studied for clusters of different size and shape. The results have been complemented by calculations of the exchange coupling parameters Jij which have been used within Monte Carlo simulations on the basis of the extended classical Heisenberg–Hamiltonian. This allowed simulation of the magnetic properties at finite temperatures, which are of central importance for technical applications of magnetic clusters.

We compute the Compton profile of Ni using the Local Density Approximation of Density Functional Theory supplemented with electronic correlations treated at different levels. The total/magnetic Compton profiles show not only quantitative but also qualitative significant differences depending weather Hubbard corrections are treated at a mean field +U or in a more sophisticated dynamic way. Our aim is to discuss the range and capability of electronic correlations to modify the kinetic energy along specific spatial directions. The second and the fourth order moments of the difference in the Compton profiles are discussed as a function of the strength of local Coulomb interaction $U$., 10 pages, 7 figs., submitted to PRB

The electronic structure and magnetic properties of the disordered alloy system fcc-FexNi1−x (fcc: face centered cubic) have been investigated by means of the KKR-CPA (Korringa–Kohn–Rostoker coherent potential approximation) band structure method. To investigate the impact of correlation effects, the calculations have been performed on the basis of the LSDA (local spin density approximation), the LSDA + U as well as the LSDA + DMFT (dynamical mean field theory). It turned out that the inclusion of correlation effects hardly changed the spin magnetic moments and the related hyperfine fields. The spin–orbit induced orbital magnetic moments and hyperfine fields, on the other hand, show a pronounced and element-specific enhancement. These findings are in full accordance with the results of a recent experimental study.

In this work, the structural and magnetic properties of Er1-xZrxFe2 (0.1 ≤ x ≤ 0.4) were investigated. These compounds crystallize in the cubic MgCu2 (C15) structure, the lattice parameters decreasing with Zr content. Electronic structure calculations were performed, showing a good agreement between theory and experiment. All of the samples are ferrimagnetically ordered, presenting compensation points in the M(T) plots. The compensation point values decrease, while the Curie temperatures increase with Zr content. The experimental Fe moments at 5 K decrease with Zr content from 1.70 μB/atom for x = 0.1 to 1.55 μB/atom for x = 0.4. A non-collinear orientation of the magnetic moments was evidenced in these compounds. The magnetocaloric effect was also studied. A modest magnetocaloric effect was found for all of the samples, spreading across a wide temperature range. A maximum |ΔSM| value of 1.19 J kg(-1) K(-1) was found for the sample with x = 0.1 for an applied field change of 0-4 T. Large RCP(ΔS) values were obtained for all of the samples, mainly due to the wide δTFWHM values of the ΔSM(T) curves.

The electronic structure and magnetic properties of CrSb${}_{2}$ have been investigated by ab initio calculations with an emphasis on the role of the magnetic structure for the ground state. The influence of correlation effects has been investigated by performing generalized gradient approximation (GGA) and GGA+U calculations showing their important role for the electronic and magnetic properties. Some details of the electronic structure of CrSb${}_{2}$ are analyzed by a comparison with those of FeSb${}_{2}$. The results obtained contribute in particular to the understanding of the temperature dependence of transport and magnetic behavior observed experimentally.

The pressure induced bcc to hcp transition in Fe has been investigated via ab-initio electronic structure calculations. It is found by the disordered local moment (DLM) calculations that the temperature induced spin fluctuations result in the decrease of the energy of Burgers type lattice distortions and softening of the transverse $N$-point $TA_1$ phonon mode with $[\bar{1}10]$ polarization. As a consequence, spin disorder in an system leads to the increase of the amplitude of atomic displacements. On the other hand, the exchange coupling parameters obtained in our calculations strongly decrease at large amplitude of lattice distortions. This results in a mutual interrelation of structural and magnetic degrees of freedom leading to the instability of the bcc structure under pressure at finite temperature.

The electronic structure and magnetic properties of Cr–Sb compounds with zinc-blende and wurtzite structure have been studied by means of the Korringa–Kohn–Rostoker (KKR) band structure method. The occurrence of a half-metallic behavior has been investigated for the bulk systems as a function of lattice parameter, as well as for thin films deposited on different substrates. In the latter case the influence of the surface and interface on the electronic structure is discussed in addition. To study magnetic order in the bulk and within the films, exchange coupling parameters have been calculated from first principles. They have been used for subsequent Monte Carlo simulations, based on a classical Heisenberg Hamiltonian, to obtain the Curie temperature.

A scheme to calculate the electronic structure of systems having a spiral magnetic structure is presented. The approach is based on the Korringa-Kohn-Rostoker Green's function formalism which allows, in combination with the coherent potential approximation alloy theory, dealing with chemically disordered materials. It is applied to the magnetic random alloys Fe${}_{x}$Ni${}_{1\ensuremath{-}x}$, Fe${}_{x}$Co${}_{1\ensuremath{-}x}$, and Fe${}_{x}$Mn${}_{1\ensuremath{-}x}$. For these systems the stability of their magnetic structure was analyzed. For Fe${}_{x}$Ni${}_{1\ensuremath{-}x}$ the spin stiffness for was determined as a function of concentration that was found in satisfying agreement with experiment. Performing spin spiral calculations the longitudinal momentum-dependent magnetic susceptibility was calculated for pure elemental systems (Cr, Ni) in the nonmagnetic state as well as for random alloys (Ag${}_{x}$Pt${}_{1\ensuremath{-}x}$). The obtained susceptibility was used to analyze the stability of the paramagnetic state of these systems.

An investigation on the electronic and magnetic properties of NiAs-type CrTe and CrSe has been performed for ferromagnetic, antiferromagnetic and non-collinear spin configurations, using the spin-polarized relativistic KKR (Korringa-Kohn-Rostoker) band structure method. Calculated exchange coupling parameters, as well as the total energy calculated as a function of the tilt angle of magnetic moments, indicate the presence of a non-collinear spin structure in CrTe and CrSe. The existence of a non-collinear spin structure is also shown by Monte Carlo (MC) simulations used for studies on the temperature dependent magnetization. The results are compared with available results in the literature and are in satisfactory agreement with the experimental results.

The magneto-crystalline anisotropy (MCA) of (Ga,Mn)As films has been studied on the basis of ab-initio electronic structure theory by performing magnetic torque calculations. An appreciable contribution to the in-plane uniaxial anisotropy can be attributed to an extended region adjacent to the surface. Calculations of the exchange tensor allow to ascribe a significant part to the MCA to the exchange anisotropy, caused either by a tetragonal distortion of the lattice or by the presence of the surface or interface., 5 pages, 3 figures

Available experimental data on the magnetic susceptibility of melt-quenched amorphous TE-TL alloys ($\mathrm{TE}=\mathrm{Ti}$ or Zr; $\mathrm{TL}=\mathrm{Ni}$ or Cu) and the corresponding crystalline counterparts are reviewed. In order to analyze the composition dependence of the magnetic susceptibility in these systems, the individual contributions (element-resolved Langevin diamagnetic, Van Vleck and Pauli spin susceptibility, as well as the Landau susceptibility) were determined directly by theoretical calculations for these TE-TL alloys in a face-centered-cubic (fcc) structure. The total susceptibility, both experimental and calculated, was found to decrease with increasing TL content up to about $60--70\phantom{\rule{0.3em}{0ex}}\mathrm{at.}\phantom{\rule{0.2em}{0ex}}%$. This variation was mainly ascribed to corresponding changes of the Van Vleck contribution and the spin susceptibility. The composition dependence of the latter term is in line with the previously established trend of variation of the density of states at the Fermi level $n({E}_{F})$ upon alloying. As in previous reports on electronic band-structure calculations, it turned out that to get agreement with experiments on $n({E}_{F})$ in amorphous Zr-Ni alloys, at least some partial chemical ordering should be taken into account. Available experimental data of crystalline stoichiometric Zr-Ni compounds beyond $70\phantom{\rule{0.3em}{0ex}}\mathrm{at.}\phantom{\rule{0.2em}{0ex}}%$ Ni show a gradual increase of the Pauli susceptibility, indicating an approach toward the onset of ferromagnetic order observed previously experimentally around $90\phantom{\rule{0.3em}{0ex}}\mathrm{at.}\phantom{\rule{0.2em}{0ex}}%$ Ni in amorphous Zr-Ni alloys. The susceptibility calculations for fcc Ti-Ni and Zr-Ni alloys indicate a strong increase of the spin susceptibility component above $70\phantom{\rule{0.3em}{0ex}}\mathrm{at.}\phantom{\rule{0.2em}{0ex}}%$ Ni, and the calculated Stoner enhancement for ${\mathrm{Zr}}_{10}{\mathrm{Ni}}_{90}$ fulfills the condition of ferromagnetism in agreement with the experimental observation.

The title compounds were prepared by reaction of Tl2Q (Q = S, Se and Te) Sc and Q in the temperature range of 200 to 500 °C. The structures of the selenide and the telluride adopt the α-NaFeO2 type, while TlScS2 crystallizes in the β-RbScO2 type structure. The space group is for TlScSe2 and TlScTe2 with a = 3.9370(4) A, c = 23.194(5) A, and a = 4.2129(4) A, c = 24.099(3) A, respectively. The sulphide crystallizes in P63/mmc with a = 3.761(3) A and c = 14.942(4) A. The crystal chemical relations between the three chalcogenides are discussed. According to the electrical measurements and the band structure calculations, the compounds are semiconductors or poor metals.

Available experimental data on the magnetic susceptibility of melt-quenched amorphous TE-TL alloys ($\mathrm{TE}=\mathrm{Ti}$ or Zr; $\mathrm{TL}=\mathrm{Ni}$ or Cu) and the corresponding crystalline counterparts are reviewed. In order to analyze the composition dependence of the magnetic susceptibility in these systems, the individual contributions (element-resolved Langevin diamagnetic, Van Vleck and Pauli spin susceptibility, as well as the Landau susceptibility) were determined directly by theoretical calculations for these TE-TL alloys in a face-centered-cubic (fcc) structure. The total susceptibility, both experimental and calculated, was found to decrease with increasing TL content up to about $60--70\phantom{\rule{0.3em}{0ex}}\mathrm{at.}\phantom{\rule{0.2em}{0ex}}%$. This variation was mainly ascribed to corresponding changes of the Van Vleck contribution and the spin susceptibility. The composition dependence of the latter term is in line with the previously established trend of variation of the density of states at the Fermi level $n({E}_{F})$ upon alloying. As in previous reports on electronic band-structure calculations, it turned out that to get agreement with experiments on $n({E}_{F})$ in amorphous Zr-Ni alloys, at least some partial chemical ordering should be taken into account. Available experimental data of crystalline stoichiometric Zr-Ni compounds beyond $70\phantom{\rule{0.3em}{0ex}}\mathrm{at.}\phantom{\rule{0.2em}{0ex}}%$ Ni show a gradual increase of the Pauli susceptibility, indicating an approach toward the onset of ferromagnetic order observed previously experimentally around $90\phantom{\rule{0.3em}{0ex}}\mathrm{at.}\phantom{\rule{0.2em}{0ex}}%$ Ni in amorphous Zr-Ni alloys. The susceptibility calculations for fcc Ti-Ni and Zr-Ni alloys indicate a strong increase of the spin susceptibility component above $70\phantom{\rule{0.3em}{0ex}}\mathrm{at.}\phantom{\rule{0.2em}{0ex}}%$ Ni, and the calculated Stoner enhancement for ${\mathrm{Zr}}_{10}{\mathrm{Ni}}_{90}$ fulfills the condition of ferromagnetism in agreement with the experimental observation.

It is demonstrated that for paramagnetic solids an external magnetic field-in analogy to the magneto-optical Kerr effect in the visible regime of light-gives rise to a magnetic circular dichroism in x-ray absorption (MCXD). A detailed description of this new field-induced magneto-optical phenomenon is given. In particular it is shown that the resulting dichroic spectra may be used to deduce the spin and orbital susceptibility in a component resolved way by making use of a modified form of the MCXD sum rules.

The electronic structure and magnetic properties of Mn1−xCrxSb alloys were investigated for the full concentration range. The stability of the concentration-dependent magnetic structure of the alloys were analysed on the basis of spin–spiral calculations as well as using the Monte Carlo (MC) simulations based on the Heisenberg model with the exchange coupling parameters calculated from first-principles. A leading contribution to the canted magnetic structure in Mn1−xCrxSb is the competition of the direct Cr–Cr and Mn–Mn exchange interactions having opposite signs. Furthermore, a strong impact of long-distance RKKY-type interactions is demonstrated. MC simulations at finite temperature were used to obtain the magnetic phase diagram for Mn1−xCrxSb alloys, which is in reasonable agreement with the experimental data.

It is demonstrated that the magnetic circular dichroism in x-ray absorption (XMCD) can be used to probe the spin and orbital high-field susceptibilities of spontaneously magnetic solids on the basis of the so-called XMCD sum rules. A corresponding theoretical description is presented that is formulated in terms of the fully relativistic multiple scattering Green's function formalism. Examples for the field-induced changes in XMCD spectra are given together with an application of the sum rules to these spectra that demonstrates their relation to the high-field susceptibility.