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Spatial inversion symmetry in crystal structures is closely related to the superconducting (SC) and magnetic properties of materials. Recently, several theoretical proposals that predict various interesting phenomena caused by the breaking of the local inversion symmetry have been presented. However, experimental validation has not yet progressed owing to the lack of model materials. Here we present evidence for antiferromagnetic (AFM) order in CeRh₂As₂ (SC transition temperature T[SC]∼0.37 K), wherein the Ce site breaks the local inversion symmetry. The evidence is based on the observation of different extents of broadening of the nuclear quadrupole resonance spectrum at two crystallographically inequivalent As sites. This AFM ordering breaks the inversion symmetry of this system, resulting in the activation of an odd-parity magnetic multipole. Moreover, the onset of antiferromagnetism T[N] within an SC phase, with T[N]

Applying in-plane uniaxial pressure to strongly correlated low-dimensional systems has been shown to tune the electronic structure dramatically. For example, the unconventional superconductor Sr2RuO4 can be tuned through a single Van Hove point, resulting in strong enhancement of both Tc and Hc2. Out-of-plane (c axis) uniaxial pressure is expected to tune the quasi-two-dimensional structure even more strongly, by pushing it towards two Van Hove points simultaneously. Here, we achieve a record uniaxial stress of 3.2 GPa along the c axis of Sr2RuO4. Hc2 increases, as expected for increasing density of states, but unexpectedly Tc falls. As a first attempt to explain this result, we present three-dimensional calculations in the weak interaction limit. We find that within the weak-coupling framework there is no single order parameter that can account for the contrasting effects of in-plane versus c-axis uniaxial stress, which makes this new result a strong constraint on theories of the superconductivity of Sr2RuO4.

Applying in-plane uniaxial pressure to strongly correlated low-dimensional systems has been shown to tune the electronic structure dramatically. For example, the unconventional superconductor Sr2RuO4 can be tuned through a single Van Hove point, resulting in strong enhancement of both T-c and H-c2. Out-of-plane (c axis) uniaxial pressure is expected to tune the quasi-two-dimensional structure even more strongly, by pushing it towards two Van Hove points simultaneously. Here, we achieve a record uniaxial stress of 3.2 GPa along the c axis of Sr2RuO4. H-c2 increases, as expected for increasing density of states, but unexpectedly T-c falls. As a first attempt to explain this result, we present three-dimensional calculations in the weak interaction limit. We find that within the weak-coupling framework there is no single order parameter that can account for the contrasting effects of in-plane versus c-axis uniaxial stress, which makes this new result a strong constraint on theories of the superconductivity of Sr2RuO4. In the superconductor Sr2RuO4, in-plane strain is known to enhance both the superconducting transition temperature Tc and upper critical field Hc2, but the effect of out-of-plane strain has not been studied. Here, the authors find that Hc2 is enhanced under out-of-plane strain, but Tc unexpectedly decreases., QC 20220830

We present inelastic neutron scattering data on the quantum paramagnet AgVOAsO4 that establish the system is a S=1/2 alternating spin chain compound and provide a direct measurement of the spin gap. We also present experimental evidence for two different types of field-induced magnetic order between μ0Hc1= 8.4 T and μ0Hc2=48.9 T, which may be related to Bose-Einstein condensation (BEC) of triplons. Thermodynamic measurements in magnetic fields up to 60 T and temperatures down to 0.1 K reveal a H−T phase diagram consisting of a dome encapsulating two ordered phases with maximum ordering temperatures of 3.8 K and 5.3 K respectively. This complex phase diagram is not expected for a single-Q BEC system and therefore establishes AgVOAsO4 as a promising multi-Q BEC candidate capable of hosting exotic vortex phases.

We present inelastic neutron scattering data on the quantum paramagnet AgVOAsO4 that establish the system is a S=1/2 alternating spin chain compound and provide a direct measurement of the spin gap. We also present experimental evidence for two different types of field-induced magnetic order between μ0Hc1= 8.4 T and μ0Hc2=48.9 T, which may be related to Bose-Einstein condensation (BEC) of triplons. Thermodynamic measurements in magnetic fields up to 60 T and temperatures down to 0.1 K reveal a H−T phase diagram consisting of a dome encapsulating two ordered phases with maximum ordering temperatures of 3.8 K and 5.3 K respectively. This complex phase diagram is not expected for a single-Q BEC system and therefore establishes AgVOAsO4 as a promising multi-Q BEC candidate capable of hosting exotic vortex phases.

We present inelastic neutron scattering data on the quantum paramagnet AgVOAsO4 that establish the system is a S=1/2 alternating spin chain compound and provide a direct measurement of the spin gap. We also present experimental evidence for two different types of field-induced magnetic order between μ0Hc1= 8.4 T and μ0Hc2=48.9 T, which may be related to Bose-Einstein condensation (BEC) of triplons. Thermodynamic measurements in magnetic fields up to 60 T and temperatures down to 0.1 K reveal a H−T phase diagram consisting of a dome encapsulating two ordered phases with maximum ordering temperatures of 3.8 K and 5.3 K respectively. This complex phase diagram is not expected for a single-Q BEC system and therefore establishes AgVOAsO4 as a promising multi-Q BEC candidate capable of hosting exotic vortex phases.

We present inelastic neutron scattering data on the quantum paramagnet AgVOAsO4 that establish the system is a S=1/2 alternating spin chain compound and provide a direct measurement of the spin gap. We also present experimental evidence for two different types of field-induced magnetic order between μ0Hc1= 8.4 T and μ0Hc2=48.9 T, which may be related to Bose-Einstein condensation (BEC) of triplons. Thermodynamic measurements in magnetic fields up to 60 T and temperatures down to 0.1 K reveal a H−T phase diagram consisting of a dome encapsulating two ordered phases with maximum ordering temperatures of 3.8 K and 5.3 K respectively. This complex phase diagram is not expected for a single-Q BEC system and therefore establishes AgVOAsO4 as a promising multi-Q BEC candidate capable of hosting exotic vortex phases.

We present inelastic neutron scattering data on the quantum paramagnet AgVOAsO4 that establish the system is a S=1/2 alternating spin chain compound and provide a direct measurement of the spin gap. We also present experimental evidence for two different types of field-induced magnetic order between μ0Hc1= 8.4 T and μ0Hc2=48.9 T, which may be related to Bose-Einstein condensation (BEC) of triplons. Thermodynamic measurements in magnetic fields up to 60 T and temperatures down to 0.1 K reveal a H−T phase diagram consisting of a dome encapsulating two ordered phases with maximum ordering temperatures of 3.8 K and 5.3 K respectively. This complex phase diagram is not expected for a single-Q BEC system and therefore establishes AgVOAsO4 as a promising multi-Q BEC candidate capable of hosting exotic vortex phases.

The magnetic, thermal and transport properties as well as electronic band structure of MnPtSi are reported. MnPtSi is a metal that undergoes a ferromagnetic transition at T_C = 340(1) K and a spin–reorientation transition at T_N = 326(1) K to an antiferromagnetic phase. First–principles electronic structure calculations indicate a not–fully polarized spin state of Mn in a d^5 electron configuration with J = S = 3/2, in agreement with the saturation magnetization of 3 µ_B per f.u. in the ordered state and the observed paramagnetic effective moment. A sizeable anomalous Hall effect in the antiferromagnetic phase alongside the computational study suggests that the antiferromagnetic structure is noncollinear. Based on thermodynamic measurements and resistivity data we construct a magnetic phase diagram. Magnetization curves M(H) at low temperatures reveal a metamagnetic transition of spin–flop type. The spin-flopped phase terminates at a critical point with T_cr ≈ 300 K and H_cr ≈ 10 kOe, near which a peak of the magnetocaloric entropy change is observed. Using Arrott plot analysis and magnetoresistivity data we argue that the metamagnetic transition is of a first–order type, whereas the strong field dependence of T_N and the linear relationship of the T_N with M^2 hint at its magnetoelastic nature.

The magnetic, thermal and transport properties as well as electronic band structure of MnPtSi are reported. MnPtSi is a metal that undergoes a ferromagnetic transition at T_C = 340(1) K and a spin–reorientation transition at T_N = 326(1) K to an antiferromagnetic phase. First–principles electronic structure calculations indicate a not–fully polarized spin state of Mn in a d^5 electron configuration with J = S = 3/2, in agreement with the saturation magnetization of 3 µ_B per f.u. in the ordered state and the observed paramagnetic effective moment. A sizeable anomalous Hall effect in the antiferromagnetic phase alongside the computational study suggests that the antiferromagnetic structure is non–collinear. Based on thermodynamic measurements and resistivity data we construct a magnetic phase diagram. Magnetization curves M(H) at low temperatures reveal a metamagnetic transition of spin–flop type. The spin-flopped phase terminates at a critical point with T_cr ≈ 300 K and H_cr ≈ 10 kOe, near which a peak of the magnetocaloric entropy change is observed. Using Arrott plot analysis and magnetoresistivity data we argue that the metamagnetic transition is of a first–order type, whereas the strong field dependence of T_N and the linear relationship of the T_N with M^2 hint at its magnetoelastic nature.

The magnetic, thermal and transport properties as well as electronic band structure of MnPtSi are reported. MnPtSi is a metal that undergoes a ferromagnetic transition at T_C = 340(1) K and a spin–reorientation transition at T_N = 326(1) K to an antiferromagnetic phase. First–principles electronic structure calculations indicate a not–fully polarized spin state of Mn in a d^5 electron configuration with J = S = 3/2, in agreement with the saturation magnetization of 3 µ_B per f.u. in the ordered state and the observed paramagnetic effective moment. A sizeable anomalous Hall effect in the antiferromagnetic phase alongside the computational study suggests that the antiferromagnetic structure is noncollinear. Based on thermodynamic measurements and resistivity data we construct a magnetic phase diagram. Magnetization curves M(H) at low temperatures reveal a metamagnetic transition of spin–flop type. The spin-flopped phase terminates at a critical point with T_cr ≈ 300 K and H_cr ≈ 10 kOe, near which a peak of the magnetocaloric entropy change is observed. Using Arrott plot analysis and magnetoresistivity data we argue that the metamagnetic transition is of a first–order type, whereas the strong field dependence of T_N and the linear relationship of the T_N with M^2 hint at its magnetoelastic nature.

The magnetic, thermal and transport properties as well as electronic band structure of MnPtSi are reported. MnPtSi is a metal that undergoes a ferromagnetic transition at T_C = 340(1) K and a spin–reorientation transition at T_N = 326(1) K to an antiferromagnetic phase. First–principles electronic structure calculations indicate a not–fully polarized spin state of Mn in a d^5 electron configuration with J = S = 3/2, in agreement with the saturation magnetization of 3 µ_B per f.u. in the ordered state and the observed paramagnetic effective moment. A sizeable anomalous Hall effect in the antiferromagnetic phase alongside the computational study suggests that the antiferromagnetic structure is non–collinear. Based on thermodynamic measurements and resistivity data we construct a magnetic phase diagram. Magnetization curves M(H) at low temperatures reveal a metamagnetic transition of spin–flop type. The spin-flopped phase terminates at a critical point with T_cr ≈ 300 K and H_cr ≈ 10 kOe, near which a peak of the magnetocaloric entropy change is observed. Using Arrott plot analysis and magnetoresistivity data we argue that the metamagnetic transition is of a first–order type, whereas the strong field dependence of T_N and the linear relationship of the T_N with M^2 hint at its magnetoelastic nature.

The magnetic, thermal and transport properties as well as electronic band structure of MnPtSi are reported. MnPtSi is a metal that undergoes a ferromagnetic transition at T_C = 340(1) K and a spin–reorientation transition at T_N = 326(1) K to an antiferromagnetic phase. First–principles electronic structure calculations indicate a not–fully polarized spin state of Mn in a d^5 electron configuration with J = S = 3/2, in agreement with the saturation magnetization of 3 µ_B per f.u. in the ordered state and the observed paramagnetic effective moment. A sizeable anomalous Hall effect in the antiferromagnetic phase alongside the computational study suggests that the antiferromagnetic structure is noncollinear. Based on thermodynamic measurements and resistivity data we construct a magnetic phase diagram. Magnetization curves M(H) at low temperatures reveal a metamagnetic transition of spin–flop type. The spin-flopped phase terminates at a critical point with T_cr ≈ 300 K and H_cr ≈ 10 kOe, near which a peak of the magnetocaloric entropy change is observed. Using Arrott plot analysis and magnetoresistivity data we argue that the metamagnetic transition is of a first–order type, whereas the strong field dependence of T_N and the linear relationship of the T_N with M^2 hint at its magnetoelastic nature.

The magnetic, thermal and transport properties as well as electronic band structure of MnPtSi are reported. MnPtSi is a metal that undergoes a ferromagnetic transition at T_C = 340(1) K and a spin–reorientation transition at T_N = 326(1) K to an antiferromagnetic phase. First–principles electronic structure calculations indicate a not–fully polarized spin state of Mn in a d^5 electron configuration with J = S = 3/2, in agreement with the saturation magnetization of 3 µ_B per f.u. in the ordered state and the observed paramagnetic effective moment. A sizeable anomalous Hall effect in the antiferromagnetic phase alongside the computational study suggests that the antiferromagnetic structure is non–collinear. Based on thermodynamic measurements and resistivity data we construct a magnetic phase diagram. Magnetization curves M(H) at low temperatures reveal a metamagnetic transition of spin–flop type. The spin-flopped phase terminates at a critical point with T_cr ≈ 300 K and H_cr ≈ 10 kOe, near which a peak of the magnetocaloric entropy change is observed. Using Arrott plot analysis and magnetoresistivity data we argue that the metamagnetic transition is of a first–order type, whereas the strong field dependence of T_N and the linear relationship of the T_N with M^2 hint at its magnetoelastic nature.

The magnetic, thermal and transport properties as well as electronic band structure of MnPtSi are reported. MnPtSi is a metal that undergoes a ferromagnetic transition at T_C = 340(1) K and a spin–reorientation transition at T_N = 326(1) K to an antiferromagnetic phase. First–principles electronic structure calculations indicate a not–fully polarized spin state of Mn in a d^5 electron configuration with J = S = 3/2, in agreement with the saturation magnetization of 3 µ_B per f.u. in the ordered state and the observed paramagnetic effective moment. A sizeable anomalous Hall effect in the antiferromagnetic phase alongside the computational study suggests that the antiferromagnetic structure is noncollinear. Based on thermodynamic measurements and resistivity data we construct a magnetic phase diagram. Magnetization curves M(H) at low temperatures reveal a metamagnetic transition of spin–flop type. The spin-flopped phase terminates at a critical point with T_cr ≈ 300 K and H_cr ≈ 10 kOe, near which a peak of the magnetocaloric entropy change is observed. Using Arrott plot analysis and magnetoresistivity data we argue that the metamagnetic transition is of a first–order type, whereas the strong field dependence of T_N and the linear relationship of the T_N with M^2 hint at its magnetoelastic nature.

The magnetic, thermal and transport properties as well as electronic band structure of MnPtSi are reported. MnPtSi is a metal that undergoes a ferromagnetic transition at T_C = 340(1) K and a spin–reorientation transition at T_N = 326(1) K to an antiferromagnetic phase. First–principles electronic structure calculations indicate a not–fully polarized spin state of Mn in a d^5 electron configuration with J = S = 3/2, in agreement with the saturation magnetization of 3 µ_B per f.u. in the ordered state and the observed paramagnetic effective moment. A sizeable anomalous Hall effect in the antiferromagnetic phase alongside the computational study suggests that the antiferromagnetic structure is noncollinear. Based on thermodynamic measurements and resistivity data we construct a magnetic phase diagram. Magnetization curves M(H) at low temperatures reveal a metamagnetic transition of spin–flop type. The spin-flopped phase terminates at a critical point with T_cr ≈ 300 K and H_cr ≈ 10 kOe, near which a peak of the magnetocaloric entropy change is observed. Using Arrott plot analysis and magnetoresistivity data we argue that the metamagnetic transition is of a first–order type, whereas the strong field dependence of T_N and the linear relationship of the T_N with M^2 hint at its magnetoelastic nature.

The magnetic, thermal and transport properties as well as electronic band structure of MnPtSi are reported. MnPtSi is a metal that undergoes a ferromagnetic transition at T_C = 340(1) K and a spin–reorientation transition at T_N = 326(1) K to an antiferromagnetic phase. First–principles electronic structure calculations indicate a not–fully polarized spin state of Mn in a d^5 electron configuration with J = S = 3/2, in agreement with the saturation magnetization of 3 µ_B per f.u. in the ordered state and the observed paramagnetic effective moment. A sizeable anomalous Hall effect in the antiferromagnetic phase alongside the computational study suggests that the antiferromagnetic structure is non–collinear. Based on thermodynamic measurements and resistivity data we construct a magnetic phase diagram. Magnetization curves M(H) at low temperatures reveal a metamagnetic transition of spin–flop type. The spin-flopped phase terminates at a critical point with T_cr ≈ 300 K and H_cr ≈ 10 kOe, near which a peak of the magnetocaloric entropy change is observed. Using Arrott plot analysis and magnetoresistivity data we argue that the metamagnetic transition is of a first–order type, whereas the strong field dependence of T_N and the linear relationship of the T_N with M^2 hint at its magnetoelastic nature.

Cuprate materials, such as those hosting high-temperature superconductivity, represent a famous class of materials where the correlations between the strongly entangled charges and spins produce complex phase diagrams. Several years ago, the Zhang-Rice singlet was proposed as a natural quasiparticle in hole-doped cuprates. The occurrence and binding energy of this quasiparticle, consisting of a pair of bound holes with antiparallel spins on the same $CuO_4$ plaquette, depends on the local electronic interactions, which are fundamental quantities for understanding the physics of the cuprates. Here, we employ state-of-the-art resonant inelastic x-ray scattering (RIXS) to probe the correlated physics of the $CuO_4$ plaquettes in the quasi-one-dimensional chain cuprate $Li_2CuO_2$. By tuning the incoming photon energy to the O K edge, we populate bound states related to the Zhang-Rice quasiparticles in the RIXS process. Both intra- and interchain Zhang-Rice singlets are observed and their occurrence is shown to depend on the nearest-neighbor spin-spin correlations, which are readily probed in this experiment. We also extract the binding energy of the Zhang-Rice singlet and identify the Zhang-Rice triplet excitation in the RIXS spectra.

A crystal structure can be understood as a result of bonding interactions (covalent, ionic, van der Waals, etc.) between the constituting atoms. If the forces caused by these interactions are equilibrated, the so-stabilized crystal structure should have the lowest energy. In such an atomic configuration, additional weaker atomic interactions may further reduce the total energy, influencing the final atomic arrangement. Indeed, in the intermetallic compound MnSiPt, a 3D framework is formed by polar covalent bonds between Mn, Si, and Pt atoms. Without taking into account the local spin polarization of manganese atoms, they would form Mn–Mn bonds within the framework. Surprisingly, the local magnetic moments of manganese prevent the formation of Mn–Mn bonds, thus changing decisively and significantly the final atomic arrangement.Among intermetallic compounds, ternary phases with the simple stoichiometric ratio 1:1:1 form one of the largest families. More than 15 structural patterns have been observed for several hundred compounds constituting this group. This, on first glance unexpected, finding is a consequence of the complex mechanism of chemical bonding in intermetallic structures, allowing for large diversity. Their formation process can be understood based on a hierarchy of energy scales: The main share is contributed by covalent and ionic interactions in accordance with the electronic needs of the participating elements. However, smaller additional atomic interactions may still tip the scales. Here, we demonstrate that the local spin polarization of paramagnetic manganese in the new compound MnSiPt rules the adopted TiNiSi-type crystal structure. Combining a thorough experimental characterization with a theoretical analysis of the energy landscape and the chemical bonding of MnSiPt, we show that the paramagnetism of the Mn atoms suppresses the formation of Mn–Mn bonds, deciding between competing crystal structures.

A crystal structure can be understood as a result of bonding interactions (covalent, ionic, van der Waals, etc.) between the constituting atoms. If the forces caused by these interactions are equilibrated, the so-stabilized crystal structure should have the lowest energy. In such an atomic configuration, additional weaker atomic interactions may further reduce the total energy, influencing the final atomic arrangement. Indeed, in the intermetallic compound MnSiPt, a 3D framework is formed by polar covalent bonds between Mn, Si, and Pt atoms. Without taking into account the local spin polarization of manganese atoms, they would form Mn–Mn bonds within the framework. Surprisingly, the local magnetic moments of manganese prevent the formation of Mn–Mn bonds, thus changing decisively and significantly the final atomic arrangement.Among intermetallic compounds, ternary phases with the simple stoichiometric ratio 1:1:1 form one of the largest families. More than 15 structural patterns have been observed for several hundred compounds constituting this group. This, on first glance unexpected, finding is a consequence of the complex mechanism of chemical bonding in intermetallic structures, allowing for large diversity. Their formation process can be understood based on a hierarchy of energy scales: The main share is contributed by covalent and ionic interactions in accordance with the electronic needs of the participating elements. However, smaller additional atomic interactions may still tip the scales. Here, we demonstrate that the local spin polarization of paramagnetic manganese in the new compound MnSiPt rules the adopted TiNiSi-type crystal structure. Combining a thorough experimental characterization with a theoretical analysis of the energy landscape and the chemical bonding of MnSiPt, we show that the paramagnetism of the Mn atoms suppresses the formation of Mn–Mn bonds, deciding between competing crystal structures.

A crystal structure can be understood as a result of bonding interactions (covalent, ionic, van der Waals, etc.) between the constituting atoms. If the forces caused by these interactions are equilibrated, the so-stabilized crystal structure should have the lowest energy. In such an atomic configuration, additional weaker atomic interactions may further reduce the total energy, influencing the final atomic arrangement. Indeed, in the intermetallic compound MnSiPt, a 3D framework is formed by polar covalent bonds between Mn, Si, and Pt atoms. Without taking into account the local spin polarization of manganese atoms, they would form Mn–Mn bonds within the framework. Surprisingly, the local magnetic moments of manganese prevent the formation of Mn–Mn bonds, thus changing decisively and significantly the final atomic arrangement.Among intermetallic compounds, ternary phases with the simple stoichiometric ratio 1:1:1 form one of the largest families. More than 15 structural patterns have been observed for several hundred compounds constituting this group. This, on first glance unexpected, finding is a consequence of the complex mechanism of chemical bonding in intermetallic structures, allowing for large diversity. Their formation process can be understood based on a hierarchy of energy scales: The main share is contributed by covalent and ionic interactions in accordance with the electronic needs of the participating elements. However, smaller additional atomic interactions may still tip the scales. Here, we demonstrate that the local spin polarization of paramagnetic manganese in the new compound MnSiPt rules the adopted TiNiSi-type crystal structure. Combining a thorough experimental characterization with a theoretical analysis of the energy landscape and the chemical bonding of MnSiPt, we show that the paramagnetism of the Mn atoms suppresses the formation of Mn–Mn bonds, deciding between competing crystal structures.

A crystal structure can be understood as a result of bonding interactions (covalent, ionic, van der Waals, etc.) between the constituting atoms. If the forces caused by these interactions are equilibrated, the so-stabilized crystal structure should have the lowest energy. In such an atomic configuration, additional weaker atomic interactions may further reduce the total energy, influencing the final atomic arrangement. Indeed, in the intermetallic compound MnSiPt, a 3D framework is formed by polar covalent bonds between Mn, Si, and Pt atoms. Without taking into account the local spin polarization of manganese atoms, they would form Mn–Mn bonds within the framework. Surprisingly, the local magnetic moments of manganese prevent the formation of Mn–Mn bonds, thus changing decisively and significantly the final atomic arrangement.Among intermetallic compounds, ternary phases with the simple stoichiometric ratio 1:1:1 form one of the largest families. More than 15 structural patterns have been observed for several hundred compounds constituting this group. This, on first glance unexpected, finding is a consequence of the complex mechanism of chemical bonding in intermetallic structures, allowing for large diversity. Their formation process can be understood based on a hierarchy of energy scales: The main share is contributed by covalent and ionic interactions in accordance with the electronic needs of the participating elements. However, smaller additional atomic interactions may still tip the scales. Here, we demonstrate that the local spin polarization of paramagnetic manganese in the new compound MnSiPt rules the adopted TiNiSi-type crystal structure. Combining a thorough experimental characterization with a theoretical analysis of the energy landscape and the chemical bonding of MnSiPt, we show that the paramagnetism of the Mn atoms suppresses the formation of Mn–Mn bonds, deciding between competing crystal structures.

A crystal structure can be understood as a result of bonding interactions (covalent, ionic, van der Waals, etc.) between the constituting atoms. If the forces caused by these interactions are equilibrated, the so-stabilized crystal structure should have the lowest energy. In such an atomic configuration, additional weaker atomic interactions may further reduce the total energy, influencing the final atomic arrangement. Indeed, in the intermetallic compound MnSiPt, a 3D framework is formed by polar covalent bonds between Mn, Si, and Pt atoms. Without taking into account the local spin polarization of manganese atoms, they would form Mn–Mn bonds within the framework. Surprisingly, the local magnetic moments of manganese prevent the formation of Mn–Mn bonds, thus changing decisively and significantly the final atomic arrangement.Among intermetallic compounds, ternary phases with the simple stoichiometric ratio 1:1:1 form one of the largest families. More than 15 structural patterns have been observed for several hundred compounds constituting this group. This, on first glance unexpected, finding is a consequence of the complex mechanism of chemical bonding in intermetallic structures, allowing for large diversity. Their formation process can be understood based on a hierarchy of energy scales: The main share is contributed by covalent and ionic interactions in accordance with the electronic needs of the participating elements. However, smaller additional atomic interactions may still tip the scales. Here, we demonstrate that the local spin polarization of paramagnetic manganese in the new compound MnSiPt rules the adopted TiNiSi-type crystal structure. Combining a thorough experimental characterization with a theoretical analysis of the energy landscape and the chemical bonding of MnSiPt, we show that the paramagnetism of the Mn atoms suppresses the formation of Mn–Mn bonds, deciding between competing crystal structures.

A crystal structure can be understood as a result of bonding interactions (covalent, ionic, van der Waals, etc.) between the constituting atoms. If the forces caused by these interactions are equilibrated, the so-stabilized crystal structure should have the lowest energy. In such an atomic configuration, additional weaker atomic interactions may further reduce the total energy, influencing the final atomic arrangement. Indeed, in the intermetallic compound MnSiPt, a 3D framework is formed by polar covalent bonds between Mn, Si, and Pt atoms. Without taking into account the local spin polarization of manganese atoms, they would form Mn–Mn bonds within the framework. Surprisingly, the local magnetic moments of manganese prevent the formation of Mn–Mn bonds, thus changing decisively and significantly the final atomic arrangement.Among intermetallic compounds, ternary phases with the simple stoichiometric ratio 1:1:1 form one of the largest families. More than 15 structural patterns have been observed for several hundred compounds constituting this group. This, on first glance unexpected, finding is a consequence of the complex mechanism of chemical bonding in intermetallic structures, allowing for large diversity. Their formation process can be understood based on a hierarchy of energy scales: The main share is contributed by covalent and ionic interactions in accordance with the electronic needs of the participating elements. However, smaller additional atomic interactions may still tip the scales. Here, we demonstrate that the local spin polarization of paramagnetic manganese in the new compound MnSiPt rules the adopted TiNiSi-type crystal structure. Combining a thorough experimental characterization with a theoretical analysis of the energy landscape and the chemical bonding of MnSiPt, we show that the paramagnetism of the Mn atoms suppresses the formation of Mn–Mn bonds, deciding between competing crystal structures.

We report on the electronic band structure, structural, magnetic, and thermal properties of Ce2Rh3Sn5. Ce LIII-edge XAS spectra give direct evidence for an intermediate valence behavior. Thermodynamic measurements reveal magnetic transitions at TN1≈2.9 K and TN2≈2.4 K. Electrical resistivity shows behavior typical for the Kondo lattices. The coexistence of magnetic order and valence fluctuations in a Kondo lattice system we attribute to a peculiar crystal structure in which Ce ions occupy two distinct lattice sites. Analysis of the structural features of Ce2Rh3Sn5, together with results of electronic band structure calculations and thermodynamic and spectroscopic data indicate that at low temperatures only Ce ions from the Ce1 sublattice adopt a stable trivalent electronic configuration and show local magnetic moments that give rise to the magnetic ordering. By contrast, our study suggests that Ce2 ions exhibit a nonmagnetic Kondo-singlet ground state. Furthermore, the valence of Ce2 ions estimated from the Ce LIII-edge XAS spectra varies between +3.18 at 6 K and +3.08 at room temperature. Thus our joined experimental and theoretical investigations classify Ce2Rh3Sn5 as a multivalent charge-ordered system.

We report on the electronic band structure, structural, magnetic, and thermal properties of Ce2Rh3Sn5. Ce LIII-edge XAS spectra give direct evidence for an intermediate valence behavior. Thermodynamic measurements reveal magnetic transitions at TN1≈2.9 K and TN2≈2.4 K. Electrical resistivity shows behavior typical for the Kondo lattices. The coexistence of magnetic order and valence fluctuations in a Kondo lattice system we attribute to a peculiar crystal structure in which Ce ions occupy two distinct lattice sites. Analysis of the structural features of Ce2Rh3Sn5, together with results of electronic band structure calculations and thermodynamic and spectroscopic data indicate that at low temperatures only Ce ions from the Ce1 sublattice adopt a stable trivalent electronic configuration and show local magnetic moments that give rise to the magnetic ordering. By contrast, our study suggests that Ce2 ions exhibit a nonmagnetic Kondo-singlet ground state. Furthermore, the valence of Ce2 ions estimated from the Ce LIII-edge XAS spectra varies between +3.18 at 6 K and +3.08 at room temperature. Thus our joined experimental and theoretical investigations classify Ce2Rh3Sn5 as a multivalent charge-ordered system.

We report on the electronic band structure, structural, magnetic, and thermal properties of Ce2Rh3Sn5. Ce LIII-edge XAS spectra give direct evidence for an intermediate valence behavior. Thermodynamic measurements reveal magnetic transitions at TN1≈2.9 K and TN2≈2.4 K. Electrical resistivity shows behavior typical for the Kondo lattices. The coexistence of magnetic order and valence fluctuations in a Kondo lattice system we attribute to a peculiar crystal structure in which Ce ions occupy two distinct lattice sites. Analysis of the structural features of Ce2Rh3Sn5, together with results of electronic band structure calculations and thermodynamic and spectroscopic data indicate that at low temperatures only Ce ions from the Ce1 sublattice adopt a stable trivalent electronic configuration and show local magnetic moments that give rise to the magnetic ordering. By contrast, our study suggests that Ce2 ions exhibit a nonmagnetic Kondo-singlet ground state. Furthermore, the valence of Ce2 ions estimated from the Ce LIII-edge XAS spectra varies between +3.18 at 6 K and +3.08 at room temperature. Thus our joined experimental and theoretical investigations classify Ce2Rh3Sn5 as a multivalent charge-ordered system.

We report on the electronic band structure, structural, magnetic, and thermal properties of Ce2Rh3Sn5. Ce LIII-edge XAS spectra give direct evidence for an intermediate valence behavior. Thermodynamic measurements reveal magnetic transitions at TN1≈2.9 K and TN2≈2.4 K. Electrical resistivity shows behavior typical for the Kondo lattices. The coexistence of magnetic order and valence fluctuations in a Kondo lattice system we attribute to a peculiar crystal structure in which Ce ions occupy two distinct lattice sites. Analysis of the structural features of Ce2Rh3Sn5, together with results of electronic band structure calculations and thermodynamic and spectroscopic data indicate that at low temperatures only Ce ions from the Ce1 sublattice adopt a stable trivalent electronic configuration and show local magnetic moments that give rise to the magnetic ordering. By contrast, our study suggests that Ce2 ions exhibit a nonmagnetic Kondo-singlet ground state. Furthermore, the valence of Ce2 ions estimated from the Ce LIII-edge XAS spectra varies between +3.18 at 6 K and +3.08 at room temperature. Thus our joined experimental and theoretical investigations classify Ce2Rh3Sn5 as a multivalent charge-ordered system.

We report on the electronic band structure, structural, magnetic, and thermal properties of Ce2Rh3Sn5. Ce LIII-edge XAS spectra give direct evidence for an intermediate valence behavior. Thermodynamic measurements reveal magnetic transitions at TN1≈2.9 K and TN2≈2.4 K. Electrical resistivity shows behavior typical for the Kondo lattices. The coexistence of magnetic order and valence fluctuations in a Kondo lattice system we attribute to a peculiar crystal structure in which Ce ions occupy two distinct lattice sites. Analysis of the structural features of Ce2Rh3Sn5, together with results of electronic band structure calculations and thermodynamic and spectroscopic data indicate that at low temperatures only Ce ions from the Ce1 sublattice adopt a stable trivalent electronic configuration and show local magnetic moments that give rise to the magnetic ordering. By contrast, our study suggests that Ce2 ions exhibit a nonmagnetic Kondo-singlet ground state. Furthermore, the valence of Ce2 ions estimated from the Ce LIII-edge XAS spectra varies between +3.18 at 6 K and +3.08 at room temperature. Thus our joined experimental and theoretical investigations classify Ce2Rh3Sn5 as a multivalent charge-ordered system.

We report on the electronic band structure, structural, magnetic, and thermal properties of Ce2Rh3Sn5. Ce LIII-edge XAS spectra give direct evidence for an intermediate valence behavior. Thermodynamic measurements reveal magnetic transitions at TN1≈2.9 K and TN2≈2.4 K. Electrical resistivity shows behavior typical for the Kondo lattices. The coexistence of magnetic order and valence fluctuations in a Kondo lattice system we attribute to a peculiar crystal structure in which Ce ions occupy two distinct lattice sites. Analysis of the structural features of Ce2Rh3Sn5, together with results of electronic band structure calculations and thermodynamic and spectroscopic data indicate that at low temperatures only Ce ions from the Ce1 sublattice adopt a stable trivalent electronic configuration and show local magnetic moments that give rise to the magnetic ordering. By contrast, our study suggests that Ce2 ions exhibit a nonmagnetic Kondo-singlet ground state. Furthermore, the valence of Ce2 ions estimated from the Ce LIII-edge XAS spectra varies between +3.18 at 6 K and +3.08 at room temperature. Thus our joined experimental and theoretical investigations classify Ce2Rh3Sn5 as a multivalent charge-ordered system.

The new phases Ca3Pt4+xGe13−y (x = 0.1; y = 0.4; space group I213; a = 18.0578(1) Å; RI = 0.063; RP = 0.083) and Yb3Pt4Ge13 (space group P42cm; a = 12.7479(1) Å; c = 9.0009(1) Å; RI = 0.061, RP = 0.117) are obtained by high-pressure, high-temperature synthesis and crystallize in new distortion variants of the Pr3Rh4Sn13 type. Yb3Pt4Ge13 features Yb in a temperature-independent non-magnetic 4f14 (Yb2+) configuration validated by X-ray absorption spectra and resonant inelastic X-ray scattering data. Ca3Pt4+xGe13−y is diamagnetic (χ0 = −5.05 × 10−6 emu mol−1). The Sommerfeld coefficient γ = 4.4 mJ mol−1 K−2 for Ca3Pt4+xGe13−y, indicates metallic properties with a low density of states at the Fermi level in good agreement with electronic structure calculation (N(EF) = 3.3 eV−1/f.u.)); the Debye temperature (θD) is 398 K., Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

Solid state physics comprises many interesting physical phenomena driven by the complex interplay of the crystal structure, magnetic and orbital degrees of freedom, quantum fluctuations and correlation. The discovery of materials which exhibit exotic phenomena like low dimensional magnetism, superconductivity, thermoelectricity or multiferroic behavior leads to various applications which even directly influence our daily live. For such technical applications and the purposive modification of materials, the understanding of the underlying mechanisms in solids is a precondition. Nowadays DFT based band structure programs become broadly available with the possibility to calculate systems with several hundreds of atoms in reasonable time scales and high accuracy using standard computers due to the rapid technical and conceptional development in the last decades. These improvements allow to study physical properties of solids from their crystal structure and support the search for underlying mechanisms of different phenomena from microscopic grounds. This thesis focuses on the theoretical description of low dimensional magnets and intermetallic compounds. We combine DFT based electronic structure and model calculations to develop the magnetic properties of the compounds from microscopic grounds. The developed, intuitive pictures were challenged by model simulations with various experiments, probing microscopic and macroscopic properties, such as thermodynamic measurements, high field magnetization, nuclear magnetic resonance or electron spin resonance experiments. This combined approach allows to investigate the close interplay of the crystal structure and the magnetic properties of complex materials in close collaboration with experimentalists. In turn, the systematic variation of intrinsic parameters by substitution or of extrinsic factors, like magnetic field, temperature or pressure is an efficient way to probe the derived models. Especially pressure allows a continu

Solid state physics comprises many interesting physical phenomena driven by the complex interplay of the crystal structure, magnetic and orbital degrees of freedom, quantum fluctuations and correlation. The discovery of materials which exhibit exotic phenomena like low dimensional magnetism, superconductivity, thermoelectricity or multiferroic behavior leads to various applications which even directly influence our daily live. For such technical applications and the purposive modification of materials, the understanding of the underlying mechanisms in solids is a precondition. Nowadays DFT based band structure programs become broadly available with the possibility to calculate systems with several hundreds of atoms in reasonable time scales and high accuracy using standard computers due to the rapid technical and conceptional development in the last decades. These improvements allow to study physical properties of solids from their crystal structure and support the search for underlying mechanisms of different phenomena from microscopic grounds. This thesis focuses on the theoretical description of low dimensional magnets and intermetallic compounds. We combine DFT based electronic structure and model calculations to develop the magnetic properties of the compounds from microscopic grounds. The developed, intuitive pictures were challenged by model simulations with various experiments, probing microscopic and macroscopic properties, such as thermodynamic measurements, high field magnetization, nuclear magnetic resonance or electron spin resonance experiments. This combined approach allows to investigate the close interplay of the crystal structure and the magnetic properties of complex materials in close collaboration with experimentalists. In turn, the systematic variation of intrinsic parameters by substitution or of extrinsic factors, like magnetic field, temperature or pressure is an efficient way to probe the derived models. Especially pressure allows a continu

Solid state physics comprises many interesting physical phenomena driven by the complex interplay of the crystal structure, magnetic and orbital degrees of freedom, quantum fluctuations and correlation. The discovery of materials which exhibit exotic phenomena like low dimensional magnetism, superconductivity, thermoelectricity or multiferroic behavior leads to various applications which even directly influence our daily live. For such technical applications and the purposive modification of materials, the understanding of the underlying mechanisms in solids is a precondition. Nowadays DFT based band structure programs become broadly available with the possibility to calculate systems with several hundreds of atoms in reasonable time scales and high accuracy using standard computers due to the rapid technical and conceptional development in the last decades. These improvements allow to study physical properties of solids from their crystal structure and support the search for underlying mechanisms of different phenomena from microscopic grounds. This thesis focuses on the theoretical description of low dimensional magnets and intermetallic compounds. We combine DFT based electronic structure and model calculations to develop the magnetic properties of the compounds from microscopic grounds. The developed, intuitive pictures were challenged by model simulations with various experiments, probing microscopic and macroscopic properties, such as thermodynamic measurements, high field magnetization, nuclear magnetic resonance or electron spin resonance experiments. This combined approach allows to investigate the close interplay of the crystal structure and the magnetic properties of complex materials in close collaboration with experimentalists. In turn, the systematic variation of intrinsic parameters by substitution or of extrinsic factors, like magnetic field, temperature or pressure is an efficient way to probe the derived models. Especially pressure allows a continu

Solid state physics comprises many interesting physical phenomena driven by the complex interplay of the crystal structure, magnetic and orbital degrees of freedom, quantum fluctuations and correlation. The discovery of materials which exhibit exotic phenomena like low dimensional magnetism, superconductivity, thermoelectricity or multiferroic behavior leads to various applications which even directly influence our daily live. For such technical applications and the purposive modification of materials, the understanding of the underlying mechanisms in solids is a precondition. Nowadays DFT based band structure programs become broadly available with the possibility to calculate systems with several hundreds of atoms in reasonable time scales and high accuracy using standard computers due to the rapid technical and conceptional development in the last decades. These improvements allow to study physical properties of solids from their crystal structure and support the search for underlying mechanisms of different phenomena from microscopic grounds. This thesis focuses on the theoretical description of low dimensional magnets and intermetallic compounds. We combine DFT based electronic structure and model calculations to develop the magnetic properties of the compounds from microscopic grounds. The developed, intuitive pictures were challenged by model simulations with various experiments, probing microscopic and macroscopic properties, such as thermodynamic measurements, high field magnetization, nuclear magnetic resonance or electron spin resonance experiments. This combined approach allows to investigate the close interplay of the crystal structure and the magnetic properties of complex materials in close collaboration with experimentalists. In turn, the systematic variation of intrinsic parameters by substitution or of extrinsic factors, like magnetic field, temperature or pressure is an efficient way to probe the derived models. Especially pressure allows a continu

The new intermetallic compound MnPtSi was synthesized, and its crystal structure was solved and refined from single-crystal X-ray diffraction data. MnPtSi crystallizes in the orthorhombic TiNiSi structure type.1 The microstructure of polycrystalline samples show strong twinning. Structural phase transitions within the AlB2 structure family were observed in similar systems (MnNiGe, MnCoGe2). Therefore, we investigated the homogeneity range and performed in-situ high-temperature diffraction measurements. No high-temperature modification was observed. Theoretical calculations to confirm the experimental founding and give an explanation for the stability of the orthorhombic structure are in process.

The new intermetallic compound MnPtSi was synthesized, and its crystal structure was solved and refined from single-crystal X-ray diffraction data. MnPtSi crystallizes in the orthorhombic TiNiSi structure type.1 The microstructure of polycrystalline samples show strong twinning. Structural phase transitions within the AlB2 structure family were observed in similar systems (MnNiGe, MnCoGe2). Therefore, we investigated the homogeneity range and performed in-situ high-temperature diffraction measurements. No high-temperature modification was observed. Theoretical calculations to confirm the experimental founding and give an explanation for the stability of the orthorhombic structure are in process.

The new intermetallic compound MnPtSi was synthesized, and its crystal structure was solved and refined from single-crystal X-ray diffraction data. MnPtSi crystallizes in the orthorhombic TiNiSi structure type.1 The microstructure of polycrystalline samples show strong twinning. Structural phase transitions within the AlB2 structure family were observed in similar systems (MnNiGe, MnCoGe2). Therefore, we investigated the homogeneity range and performed in-situ high-temperature diffraction measurements. No high-temperature modification was observed. Theoretical calculations to confirm the experimental founding and give an explanation for the stability of the orthorhombic structure are in process.

The new intermetallic compound MnPtSi was synthesized, and its crystal structure was solved and refined from single-crystal X-ray diffraction data. MnPtSi crystallizes in the orthorhombic TiNiSi structure type.1 The microstructure of polycrystalline samples show strong twinning. Structural phase transitions within the AlB2 structure family were observed in similar systems (MnNiGe, MnCoGe2). Therefore, we investigated the homogeneity range and performed in-situ high-temperature diffraction measurements. No high-temperature modification was observed. Theoretical calculations to confirm the experimental founding and give an explanation for the stability of the orthorhombic structure are in process.

Over the last years, intermetallic compounds from the system Ce–Rh–Sn have attracted a considerable attention owing to a rich variety of strongly correlated electron phenomena they exhibit. CeRhSn2, Ce5Rh4Sn10, Ce2Rh3Sn5 and Ce3Rh4Sn13 are magnetically ordered heavy fermion systems [1-5]. Interestingly, for Ce3+xRh4Sn13-x (0.2

Over the last years, intermetallic compounds from the system Ce–Rh–Sn have attracted a considerable attention owing to a rich variety of strongly correlated electron phenomena they exhibit. CeRhSn2, Ce5Rh4Sn10, Ce2Rh3Sn5 and Ce3Rh4Sn13 are magnetically ordered heavy fermion systems [1-5]. Interestingly, for Ce3+xRh4Sn13-x (0.2

Over the last years, intermetallic compounds from the system Ce–Rh–Sn have attracted a considerable attention owing to a rich variety of strongly correlated electron phenomena they exhibit. CeRhSn2, Ce5Rh4Sn10, Ce2Rh3Sn5 and Ce3Rh4Sn13 are magnetically ordered heavy fermion systems [1-5]. Interestingly, for Ce3+xRh4Sn13-x (0.2

Over the last years, intermetallic compounds from the system Ce–Rh–Sn have attracted a considerable attention owing to a rich variety of strongly correlated electron phenomena they exhibit. CeRhSn2, Ce5Rh4Sn10, Ce2Rh3Sn5 and Ce3Rh4Sn13 are magnetically ordered heavy fermion systems [1-5]. Interestingly, for Ce3+xRh4Sn13-x (0.2

Over the last years, intermetallic compounds from the system Ce–Rh–Sn have attracted a considerable attention owing to a rich variety of strongly correlated electron phenomena they exhibit. CeRhSn2, Ce5Rh4Sn10, Ce2Rh3Sn5 and Ce3Rh4Sn13 are magnetically ordered heavy fermion systems [1-5]. Interestingly, for Ce3+xRh4Sn13-x (0.2

Over the last years, intermetallic compounds from the system Ce–Rh–Sn have attracted a considerable attention owing to a rich variety of strongly correlated electron phenomena they exhibit. CeRhSn2, Ce5Rh4Sn10, Ce2Rh3Sn5 and Ce3Rh4Sn13 are magnetically ordered heavy fermion systems [1-5]. Interestingly, for Ce3+xRh4Sn13-x (0.2

The goal of solid state physics and chemistry is to gain deeper understanding of the basic principles of condensed matter. This ongoing process is achieved by the combination of experimental methods and theoretical models. One theoretical approach are the so-called first-principles calculations, which are based on the concept of density functional theory (DFT). In order to test the reliability of a band structure calculation, its results have to be compared with experiments. Since the electron density, the main constituent of DFT codes, cannot be directly determined experimentally with sufficient accuracy (e.g., by X-ray diffraction), other experimentally available properties are needed for the comparison with the calculation. A quantity that can be measured with high accuracy and that provides indirect information about the electron density is the electric field gradient (EFG). The EFG reflects local structural symmetry properties of the charge distribution surrounding a nucleus: the EFG is nonzero if the density deviates from cubic symmetry and therefore generates an inhomogeneous electric field at the nucleus. Since the EFG is highly sensitive to structural parameters and to disorder, it is a valuable tool to extract structural information. Furthermore, the evaluation of the EFG can provide valuable insight into the chemical bonding. Whereas the experimental determination of the quadrupole frequency and the closely related EFG has been possible for more than 70 years, reliable values for calculated EFGs could not be obtained before 1985, when an EFG module was implemented in the full-potential, linearised-augmented-plane-wave code WIEN. Since the full-potential local-orbital minimum-basis scheme FPLO is numerically very efficient and its local-orbital scheme allows an easy analysis of the different contributions to the EFG, one goal of this work was the implementation of an EFG module within the FPLO code. The newly implemented EFG module was applied to different

The goal of solid state physics and chemistry is to gain deeper understanding of the basic principles of condensed matter. This ongoing process is achieved by the combination of experimental methods and theoretical models. One theoretical approach are the so-called first-principles calculations, which are based on the concept of density functional theory (DFT). In order to test the reliability of a band structure calculation, its results have to be compared with experiments. Since the electron density, the main constituent of DFT codes, cannot be directly determined experimentally with sufficient accuracy (e.g., by X-ray diffraction), other experimentally available properties are needed for the comparison with the calculation. A quantity that can be measured with high accuracy and that provides indirect information about the electron density is the electric field gradient (EFG). The EFG reflects local structural symmetry properties of the charge distribution surrounding a nucleus: the EFG is nonzero if the density deviates from cubic symmetry and therefore generates an inhomogeneous electric field at the nucleus. Since the EFG is highly sensitive to structural parameters and to disorder, it is a valuable tool to extract structural information. Furthermore, the evaluation of the EFG can provide valuable insight into the chemical bonding. Whereas the experimental determination of the quadrupole frequency and the closely related EFG has been possible for more than 70 years, reliable values for calculated EFGs could not be obtained before 1985, when an EFG module was implemented in the full-potential, linearised-augmented-plane-wave code WIEN. Since the full-potential local-orbital minimum-basis scheme FPLO is numerically very efficient and its local-orbital scheme allows an easy analysis of the different contributions to the EFG, one goal of this work was the implementation of an EFG module within the FPLO code. The newly implemented EFG module was applied to different

The goal of solid state physics and chemistry is to gain deeper understanding of the basic principles of condensed matter. This ongoing process is achieved by the combination of experimental methods and theoretical models. One theoretical approach are the so-called first-principles calculations, which are based on the concept of density functional theory (DFT). In order to test the reliability of a band structure calculation, its results have to be compared with experiments. Since the electron density, the main constituent of DFT codes, cannot be directly determined experimentally with sufficient accuracy (e.g., by X-ray diffraction), other experimentally available properties are needed for the comparison with the calculation. A quantity that can be measured with high accuracy and that provides indirect information about the electron density is the electric field gradient (EFG). The EFG reflects local structural symmetry properties of the charge distribution surrounding a nucleus: the EFG is nonzero if the density deviates from cubic symmetry and therefore generates an inhomogeneous electric field at the nucleus. Since the EFG is highly sensitive to structural parameters and to disorder, it is a valuable tool to extract structural information. Furthermore, the evaluation of the EFG can provide valuable insight into the chemical bonding. Whereas the experimental determination of the quadrupole frequency and the closely related EFG has been possible for more than 70 years, reliable values for calculated EFGs could not be obtained before 1985, when an EFG module was implemented in the full-potential, linearised-augmented-plane-wave code WIEN. Since the full-potential local-orbital minimum-basis scheme FPLO is numerically very efficient and its local-orbital scheme allows an easy analysis of the different contributions to the EFG, one goal of this work was the implementation of an EFG module within the FPLO code. The newly implemented EFG module was applied to different

The goal of solid state physics and chemistry is to gain deeper understanding of the basic principles of condensed matter. This ongoing process is achieved by the combination of experimental methods and theoretical models. One theoretical approach are the so-called first-principles calculations, which are based on the concept of density functional theory (DFT). In order to test the reliability of a band structure calculation, its results have to be compared with experiments. Since the electron density, the main constituent of DFT codes, cannot be directly determined experimentally with sufficient accuracy (e.g., by X-ray diffraction), other experimentally available properties are needed for the comparison with the calculation. A quantity that can be measured with high accuracy and that provides indirect information about the electron density is the electric field gradient (EFG). The EFG reflects local structural symmetry properties of the charge distribution surrounding a nucleus: the EFG is nonzero if the density deviates from cubic symmetry and therefore generates an inhomogeneous electric field at the nucleus. Since the EFG is highly sensitive to structural parameters and to disorder, it is a valuable tool to extract structural information. Furthermore, the evaluation of the EFG can provide valuable insight into the chemical bonding. Whereas the experimental determination of the quadrupole frequency and the closely related EFG has been possible for more than 70 years, reliable values for calculated EFGs could not be obtained before 1985, when an EFG module was implemented in the full-potential, linearised-augmented-plane-wave code WIEN. Since the full-potential local-orbital minimum-basis scheme FPLO is numerically very efficient and its local-orbital scheme allows an easy analysis of the different contributions to the EFG, one goal of this work was the implementation of an EFG module within the FPLO code. The newly implemented EFG module was applied to different

We report on the electronic structure and magnetic properties of the Kondo lattice system CeRhSn2 and of the reference compound LaRhSn2 . The Ce 3d and 4d x-ray photoemission spectroscopy (XPS) data point to a stable configuration of the Ce 4f shell in CeRhSn2 . The ac magnetic susceptibility measurements reveal two magnetic transitions for CeRhSn 2 at temperatures T_C1 = 4 K and T_C2 = 3 K. The temperature dependences of the ac susceptibility show also broad maxima at about 17 and 15 K for CeRhSn2 and LaRhSn2 , respectively. Such features hint at spin fluctuations on Rh atoms. To get detailed insight into the electronic structure of both CeRhSn2 and LaRhSn2 we perform ab initio band structure calculations within the local (spin) density approximation (L(S)DA) and using the LSDA+U approach to account for the strong Coulomb interactions within the Ce 4f shell. The LSDA+ U approximation gives qualitatively the correct physical picture of Ce3+ in CeRhSn2 . The reliability of the theoretical results is confirmed by the comparison of the calculated XPS valence band spectra with experimental data. A Fermi surface analysis shows that there are some parallel sections of the sheets, which could generate 'nesting' instabilities. These nesting features might be responsible for the spin fluctuations suggested by the ac susceptibility measurements.