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Lithium-rich antiperovskite promise to be a compelling high-capacity cathode material due to existence of both cationic and anionic redox activity. Little is however known about the effect of separating the electrochemical cationic from the anionic process and the associated implications on the electrochemical performance. In this context, we report the electrochemical properties of the illustrative example of three different Li$_2$Fe)SO materials with a focus on separating cationic from anionic effects. With the high voltage anionic process, an astonishing electrochemical capacity of around 400~mAh/g can initially be reached. Our results however identify the anionic process as the cause of poor cycling stability and demonstrate that fading reported in previous literature is avoided by restricting to only the cationic processes. Following this path, our Li$_2$Fe)SO-BM500 shows strongly improved performance indicated by constant electrochemical cycling over 100 cycles at a capacity of around 175~mAh/g at 1~C. Our approach also allows us to investigate the electrochemical performance of the bare antiperovskite phase excluding extrinsic activity from initial or cycling-induced impurity phases. Our results underscore that synthesis conditions are a critical determinant of electrochemical performance in lithium-rich antiperovskites, especially with regard to the amount of electrochemical secondary phases, while the particle size has not been found a crucial parameter. Overall, separating and understanding the effects of cationic from anionic redox activity in lithium-rich antiperovskites provides the route to further improve their performance in electrochemical energy storage.

We report high-resolution dilatometry studies on single crystals of the Shastry-Sutherland-lattice magnet NdB$_4$ supported by specific heat and magnetometry data. Our dilatometric studies evidence pronounced anomalies at the phase boundaries which imply strong magneto-elastic coupling. The evolution of the three zero-field phase transitions separating distinct antiferromagnetic phases at $TN=17.2$~K, $TIT=6.8$~K and $TLT=4.8$~K can thus be traced in applied magnetic fields which provides the magnetic phase diagrams for $B\parallel c$ up to 15~T and for $B\parallel [110]$ up to 35~T. New in-field phases are discovered for both field directions and already known phases are confirmed. In particular, phase boundaries between different phases are unambiguously shown by sign changes of observed anomalies and corresponding changes in uniaxial pressure effects. For $B||c$, we find a 1/4-magnetization plateau in addition to a previously reported plateau at 1/5 of the saturation magnetization. TN increases for $B\parallel c$ in fields up to 15~T implying that magnetic moments of the all-in/all-out structure in the high temperature AFM ordered phase are driven towards the $c$ axis in high magnetic fields. Uniaxial pressure dependencies ${\partial}T_{\mathrm{crit}}/{\partial}p_{\mathrm{c}}$ of the phase transition temperatures for magnetic fields and pressure applied along the $c$ axis are derived from the data.

Single crystals of Ruddlesden-Popper nickelates La$_4$Ni$_3$O$_{10}$ were grown by means of the floating-zone technique at oxygen pressure of 20~bar. Our results reveal the effects of the annealing process under pressure on the crystal structure. We present the requirements for crystal growth and show how a reported ferromagnetic impurity phase can be avoided. The different growth and post-annealing processes result in two distinct phases $P2_1/a$ and {\it Bmab} in which the metal-to-metal transitions occur at 152~K and 136~K, respectively.

We report the high-pressure optical floating-zone growth of GdInO$_3$ single crystals and show its magnetic phase diagram down to the mK-regime as determined by magnetization measurements. The centered-honeycomb lattice structure shows considerable magnetic frustration ($\lvert\Theta\rvert /T_{\rm N}\simeq 5$) and develops long-range magnetic order below $T_{\rm N}$~=~2.1 K from a short-range ordered paramagnetic phase. Concomitantly, a small net magnetic moment evolves at $T_{\rm N}$ which points along the crystallographic $c$ direction. Upon cooling, the net moment reorients at $T^{**}\simeq 1.7$ K and $T^{*}\simeq 1$ K. A broad 1/3 plateau indicative of the up-up-down ($uud$) spin configuration appears for $B||c$ but is absent for $B||ab$, thereby suggesting easy axis anisotropy. At $T=0.4$ K, a jump in magnetization at $\simeq 3/5$ of the saturation magnetization signals a discontinuous transition to a high field phase and we find evidence for a possible tricritical point. Small energy and field scales in the accessible regimes render GdInO$_3$ a prime example to study the phase diagram of a semiclassical frustrated hexagonal lattice in the presence of weak easy axis anisotropy of mainly dipolar origin.

We report the ground state magnetic structure and in-field magnetostrictive effects of NiTiO$_3$ studied by means of zero field and in-field single-crystal neutron diffraction, magnetization, and high-resolution dilatometry experiments. Zero-field neutron diffraction on NiTiO$_3$ single crystals reveals an easy-plane antiferromagnet with a multidomain ground state. Upon application of external magnetic fields, neutron diffraction shows the evolution of domains with spins perpendicular to the applied field. The rotation of spins in the multidomain state exhibits pronounced lattice changes in the magnetostriction measurements. We see magnetization and magnetostriction measurements sale with each other in the multidomain state revealing the strong coupling of spins to the lattice.

In this work we revisit the phase diagram of Co-doped LaFeAsO using single crystals and thermodynamic methods. From magnetic susceptibility studies we track the doping evolution of the antiferromagnetic phase, revealing a continuous suppression of $T_\mathrm{N}$ up to 5$\%$ Co doping. In order to study the evolution of the so-called nematic phase, the temperature dependence of the lengths changes along the $a$ and $b$ orthorhombic directions, $\Delta L/L_0$, was determined by high-resolution capacitance dilatometry. The results clearly show a gradual reduction of the orthorhombic distortion $\delta$ and of $T_\mathrm{S}$ with increasing Co content up to 4.5$\%$, while it is completely suppressed for 7.5$\%$ Co. Bulk superconductivity was found in a small doping region around 6$\%$ Co content, while both $T_\mathrm{c}$ and the superconducting volume fraction rapidly drop in the neighbouring doping regime. Ultimately, no microscopic coexistence between the superconducting and magnetic phases can be assessed within our resolution limit, in sharp contrast with other iron-pnictide families, e.g., electron- and hole-doped BaFe$_2$As$_2$.

The high-pressure optical floating-zone method enables single crystal growth of the Pmnb high-temperature phase of Li2FeSiO4. The influence of growth conditions on crystal quality, phase homogeneity, and impurity formation in Li2FeSiO4 is studied. The use of different starting materials, i.e., either the P121/n1 or the Pmn21 polymorph, as well as optimization of various growth conditions is investigated. Several mm3-sized high-quality single crystals are obtained by the choice of the Pmn21 polymorph as the starting material. A general challenge of Li2FeSiO4 crystal growth is polymorph control during crystallization. While the temperature gradient at the solid-liquid interface seems to have significant impact on stabilizing the Pmnb high-temperature phase, growth velocity has no evident effect.

We report high-resolution capacitance dilatometry studies on the uniaxial length changes in a NdB$_4$ single crystal. The evolution of magnetically ordered phases below $T_{\rm N}$= 17.2~K (commensurate antiferromagnetic phase, cAFM), $T_{\rm IT}$= 6.8~K (intermediate incommensurate phase, IT), and $T_{\rm LT}$= 4.8~K (low-temperature phase, LT) is associated with pronounced anomalies in the thermal expansion coefficients. The data imply significant magneto-elastic coupling and evidence of a structural phase transition at $T_{\rm LT}$ . While both cAFM and LT favor structural anisotropy $\delta$ between in-plane and out-of-plane length changes, it competes with the IT-type of order, i.e., $\delta$ is suppressed in that phase. Notably, finite anisotropy well above $T_{\rm N}$ indicates short-range correlations which are, however, of neither cAFM, IT, nor LT-type. Gr\"uneisen analysis of the ratio of thermal expansion coefficient and specific heat enables the derivation of uniaxial as well as hydrostatic pressure dependencies. While $\alpha$/$c_{\rm p}$ evidences a single dominant energy scale in LT, our data imply precursory fluctuations of a competing phase in IT and cAFM, respectively. Our results suggest the presence of orbital degrees of freedom competing with cAFM and successive evolution of a magnetically and orbitally ordered ground state.

We investigate the low temperature structural and physical properties of the trilayer nickelates R4Ni3O10 (R = La, Pr and Nd) using resistivity, thermopower, thermal conductivity, specific heat, high-resolution synchrotron powder X-ray diffraction and thermal expansion experiments. We show that all three compounds crystallize with a monoclinic symmetry, and undergo a metal-to-metal (MMT) transition at 135 K (La), 156 K (Pr) and 160 K (Nd). At MMT, the lattice parameters show distinct anomalies; however, without any lowering of the lattice symmetry. Unambiguous signatures of MMT are also seen in magnetic and thermal measurements, which suggest a strong coupling between the electronic, magnetic and structural degrees of freedom in these nickelates. Analysis of thermal expansion yields hydrostatic pressure dependence of MMT in close agreement with experiments. We show that the 9-fold coordinated Pr ions in the rocksalt (RS) layers have a crystal field (CF) split doublet ground state with possible antiferromagnetic ordering at 5 K. The Pr ions located in the perovskite block (PB) layers with 12-fold coordination, however, exhibit a non-magnetic singlet ground state. The CF ground state of Nd in both RS and PB layers is a Kramers doublet. Heat capacity of R = Nd shows a Schottky-like anomaly near35 K, and an upturn below T = 10 K suggesting the presence of short-range correlations between the Nd moments. However, no signs of long-range ordering could be found down to 2 K despite a sizeable theta_p ~ -40 K. The strongly suppressed magnetic long-range ordering in both R = Pr and Nd suggests the presence of strong magnetic frustration in these compounds. The low-temperature resistivity shows a T^0.5 dependence. No evidence for the heavy fermion behavior could be found in any of the three compounds., Comment: 19 pages, 17 figures, SI available with the authors

Downsizing well-established materials to the nanoscale is a key route to novel functionalities, in particular if different functionalities are merged in hybrid nanomaterials. Hybrid carbon-based hierarchical nanostructures are particularly promising for electrochemical energy storage since they combine benefits of nanosize effects, enhanced electrical conductivity and integrity of bulk materials. We show that endohedral multiwalled carbon nanotubes (CNT) encapsulating high-capacity (here: conversion and alloying) electrode materials have a high potential for use in anode materials for lithium-ion batteries (LIB). There are two essential characteristics of filled CNT relevant for application in electrochemical energy storage: (1) rigid hollow cavities of the CNT provide upper limits for nanoparticles in their inner cavities which are both separated from the fillings of other CNT and protected against degradation. In particular, the CNT shells resist strong volume changes of encapsulates in response to electrochemical cycling, which in conventional conversion and alloying materials hinders application in energy storage devices. (2) Carbon mantles ensure electrical contact to the active material as they are unaffected by potential cracks of the encapsulate and form a stable conductive network in the electrode compound. Our studies confirm that encapsulates are electrochemically active and can achieve full theoretical reversible capacity. The results imply that encapsulating nanostructures inside CNT can provide a route to new high-performance nanocomposite anode materials for LIB., Comment: Invited

We report high-resolution dilatometry on high-quality single crystals of NiTiO3 grown by means of the optical floating-zone technique. The anisotropic magnetic phase diagram is constructed from thermal expansion and magnetostriction studies up to B=15T and magnetization studies in static (15T) and pulsed (60T) magnetic fields. Our data allow to quantitatively study magneto-elastic coupling and to determine uniaxial pressure dependencies. While the entropy changes are found to be of magnetic nature, Gr\"{u}neisen analysis implies only one relevant energy scale in the whole low-temperature regime. Thereby, our data suggest that the observed structural changes due to magneto-elastic coupling and previously reported magnetodielectric coupling[1] are driven by the same $magnetic$ degrees of freedom that lead to long-range magnetic order in NiTiO3, which in turn, establishes a linear magnetodielectric coupling in this compound.

We report AC-impedance studies on a series of high-quality LiMn$_{1-x}$Fe$_x$PO$_4$ single crystals with $0\leq x \leq 1$. Our results confirm quasi-one-dimensional transport in LiFePO$_4$ with fast Li-diffusion along the $b$-axis. The conductivities along the crystallographic $b$-, $c$- and $a$-axis differ by a factor of about 10, respectively. Whereas, the activation energy $E_{\rm A}$ of the effective diffusion process is particularly large for the $b$-axis and smallest for the $a$-axis. Remarkably, the $b$-axis ionic bulk conductivity of LiMn$_{0.5}$Fe$_{0.5}$PO$_4$ is of the same order of magnitude as in undoped LiFePO$_4$, which implies similarly fast Li-transport even upon 50~\% Mn-doping which, owing to the higher redox potential of the Mn$^{3+}$/Mn$^{2+}$-couple, yields enhanced energy density in lithium-ion batteries. The overall results of our impedance studies draw a far more complex picture than it would be expected from a simple one-dimensional ionic conductor. Our results suggest a strong contribution of crystal defects in real materials.

The current family of experimentally realized two-dimensional magnetic materials consist of 3$d$ transition metals with very weak spin-orbit coupling. In contrast, we report a new platform in a chemically bonded and layered 4$d$ oxide, with strong electron correlations and competing spin-orbit coupling. We synthesize ultra-thin sheets of SrRu$_2$O$_6$ using scalable liquid exfoliation. These exfoliated sheets are characterized by complementary experimental and theoretical techniques. The thickness of the nano-sheets varies between three to five monolayers, and within the first-principles calculations, we show that antiferromagnetism survives in these ultra-thin layers. Experimental data suggest that exfoliation occurs from the planes perpendicular to the $c$-axis as the intervening hexagonal Sr-lattice separates the two-dimensional magnetic honeycomb Ru-layers. The high-resolution transmission electron microscope images indicate that the average inter-atomic spacing between the Ru-layers is slightly reduced, which agrees with the present calculations. The signatures of rotational stacking of the nanosheets are also observed. Such new two-dimensional platform offers enormous possibilities to explore emergent properties that appear due to the interplay between magnetism, strong correlations and spin-orbit coupling. Moreover, these effects can be further tuned as a function of layer thickness.

We report the growth of mm-sized Pmnb-Li2FeSiO4 single crystals by means of the optical floating-zone method at high argon pressure and describe the conditions required for a stable growth process. The crystal structure is determined and refined by single-crystal X-ray diffraction. The lattice constants amount to a = 6.27837(3) A, b = 10.62901(6) A and c = 5.03099(3) A at 100 K. In addition, we present high-resolution neutron powder diffraction data that suggest that the slight Li-Fe site exchange seems to be intrinsic to this material. High quality of the crystal is confirmed by very sharp anomalies in the static magnetic susceptibility and in the specific heat associated with the onset of long-range antiferromagnetic order at TN = 17.0(5) K and pronounced magnetic anisotropy for the three crystallographic axes. Furthermore, magnetic susceptibility excludes the presence of sizable amounts of magnetic impurity phases.

A macroscopic single crystal of $\gamma_{\rm II}$-Li\(_2\)FeSiO\(_4\) has been grown by means of the high-pressure optical floating-zone technique. Static magnetic susceptibility $\chi$ implies that the tetrahedrally-coordinated Fe$^{2+}$ ions are in the high-spin, $S=2$, state. While a sharp decrease in $\chi$ implies long-range antiferromagnetic order below \tn\ = 17.0(5)~K, the presence of a broad maximum at $T_{\rm m} = 28$~K suggests quasi-low-dimensional magnetism. Applying magnetic fields along the easy magnetic $a$-axis yields additional contributions to the susceptibility $\partial M/\partial B$ and magnetostriction for $B > 7$~T, and an anomaly at $B\approx 14.8$~T.

Thermodynamic properties as well as low-energy magnon excitations of $S=1$ honeycomb-layered Na$_3$Ni$_2$SbO$_6$ have been investigated by high-resolution dilatometry, static magnetisation, and high-frequency electron spin resonance studies in magnetic fields up to 16 T. At $T_{\rm N}$ = 16.5 K, there is a tricritical point separating two distinct antiferromagnetic phases AF1 and AF2 from the paramagnetic regime. In addition, our data imply short-range antiferromagnetic correlations at least up to $\sim 5\cdot T_{\rm N}$. Well below $T_{\rm N}$, the magnetic field $B_{\rm C1}\approx$ 9.5 T is needed to stabilize AF2 against AF1. The thermal expansion and magnetostriction anomalies at $T_{\rm N}$ and $B_{\rm C1}$ imply significant magnetoelastic coupling, both of which associated with a sign change of $\partial L/\partial B$. The transition at $B_{\rm C1}$ is associated with softening of the antiferromagnetic resonance modes observed in the electron spin resonance spectra. The anisotropy gap $\Delta = 360$ GHz implies considerable uniaxial anisotropy. We conclude the crucial role of axial anisotropy favoring the AF1 spin structure over the AF2 one. While the magnetostriction data disprove a simple spin-flop scenario at $B_{\rm C1}$, the nature of a second transition at $B_{\rm C2}\approx$ 13 T remains unclear. Both the sign of the magnetostriction and Gr\"uneisen analysis suggest the short-range correlations at high temperatures to be of AF2-type.

Mm-sized LiMn$_{1-x}$Fe$_x$PO$_4$ single crystals with $0\leq x \leq 1$ were grown by means of the traveling floating-zone technique at elevated Argon pressure of 30~bar. For the various doping levels, the growth process was optimized with respect to the composition-dependant effective light absorption and transparency of the materials. A convex crystal/melt interface, determined by the angle of incident light, was identified to be particularly crucial for a successful growth. The resulting large single crystalline grains are stoichiometric. Structure refinement shows that lattice parameters as well as the atomic positions and bond lengths linearly depend on the Mn:Fe-ratio. Oriented cuboidal samples with several mm$^3$ of volume were used for magnetic studies which imply an antiferromagnetic ground state for all compositions. The N\'eel-temperature changes from $T_N$ = 32.5(5) K in LiMnPO$_4$ to 49.5(5) K in LiFePO$_4$ while the easy magnetic axis in the ordered phase flips from the crystallographic $a$- to the $b$-axis upon Fe-doping of $x<0.2$.

Precise thermal expansion and magnetostriction studies of the intermetallic compound Eu$_2$CuSi$_3$ in the temperature range between 5 and 300 K are presented. A clear sign of magnetic second order phase transition at the ferromagnetic Curie temperature $T_{\rm C}$ = 34 K indicates strong magneto-structural coupling. Uniaxial thermal expansion data show a large anisotropy between the magnetic easy $c$-axis and the hexagonal $ab$-plane, which is associated with a strongly anisotropic magnetic coupling. A spin-reorientation regime as well as a non-uniform energy scale are indicated by Gr\"uneisen analysis of the data at low temperatures. Anomalous contributions to the thermal expansion imply ferromagnetic correlations far above in zero magnetic field. The magnetic phase diagram is constructed, showing the evolution of short- and long-range magnetic order in magnetic fields up to 15 T. The anisotropic magnetic field effect yields anomalous magnetostrictive effects up to about 200 K.

A uniformly coated MoS2/Carbon-nanocomposite with three-dimensional hierarchical architecture based on carbonized bacterial cellulose (CBC) nanofibers is synthesized by a facile one-step hydrothermal method followed by thermal annealing at 700 {\deg}C in Ar atmosphere. Strong hydrogen bonds between the Mo precursor and the BC nanofibers are found to be crucial for the in-situ growth of MoS2 nanosheets on the nanofibers during hydrothermal process. The unique structure was maintained and the connection between MoS2 and nanofibers were strengthened in the sintering process, leading to an improved stability of the resulting nanocomposite upon electrochemical cycling. The low-cost and environmentally friendly 3D web-like structure enables binder-free and carbon-free electrodes for lithium-ion batteries, which exhibit high specific discharge capacities up to 1140 mAh/g at the C-rate of 1 C without significant capacity fading for over 50 cycles. The porous conductive hierarchical structure of the composite endows excellent rate performance by avoiding the aggregation of the MoS2 nanosheets and by accommodating mechanical stress which appears upon electrochemical cycling.

Hierarchical C@MoS2@C hollow spheres with the active MoS2 nanosheets being sandwiched by carbon layers have been produced by means of a modified template method. The process applies polydopamine (PDA) layers which inhibit morphology change of the template thereby enforcing the hollow microsphere structure. In addition, PDA forms complexes with the Mo precursor, leading to an in-situ growth of MoS2 on its surface and preventing the nanosheets from agglomeration. It also supplies the carbon that finally sandwiches the 100-150 nm thin MoS2 spheres. The resulting hierarchically structured material provides a stable microstructure where carbon layers strongly linked to MoS2 offer efficient pathways for electron and ion transfer, and concomitantly buffer the volume changes inevitably appearing during the charge-discharge process. Carbon-sandwiched MoS2-based electrodes exhibit high specific capacity of approximately 900 mA h g-1 after 50 cycles at 0.1 C, excellent cycling stability up to 200 cycles, and superior rate performance. The versatile synthesis method reported here offers a general route to design hollow sandwich structures with a variety of different active materials.

Spherical NiPt@C nanoalloys encapsulated in carbon shells are synthesized by means of high-pressure chemical vapour deposition. Upon variation of the synthesis parameters, both the alloy core composition and the particle size of the resulting spherical NixPt1-x@C nanocapsules can be controlled. The sublimation temperatures of the Ni- and Pt-precursors are found key to control the alloy composition and diameter. Depending on the synthesis parameters, the diameters of the cores are tuneable in the range of 3 - 15 nm while the carbon coatings for all conditions are 1 - 2 nm. The core particle size decreases linearly upon increasing either of the sublimation temperatures while the Ni and Pt content, respectively, are linearly increasing with the related precursor temperature. Accordingly, the magnetic properties of the nanoalloys, i.e. magnetization, remanent magnetization and critical field, are well controlled by the two sublimation temperatures. As compared to bulk NiPt, our data show an increase of Stoner enhancement by nanoscaling as ferromagnetism appears in the Pt rich NiPt nanoalloy which is not observed for the related bulk alloys. The magneto-crystalline anisotropy constants K are in the range of 0.3 - 4 x 105 J/m3 underlining that NiPt@C is a stable, highly magnetic functional nanomaterial.

The structure and the magnetic properties of layered Li3Cu2SbO6 are investigated by powder X-ray diffraction, static susceptibility, and electron spin resonance studies up to 330 GHz. The XRD data experimentally verify the space group C2/m with halved unit cell volume in contrast to previously reported C2/c. In addition, the data show significant Li/Cu-intersite exchange. Static magnetic susceptibility and ESR measurements show two magnetic contributions, i.e. quasi-free spins at low-temperature and a spin-gapped magnetic subsystem, with about half of the spins being associated to each subsystem. The data suggest ferromagnetic-antiferromagnetic alternating chains with JFM = -285 K and JAFM = 160 K with a significant amount of Li-defects in the chains. The results are discussed in the scenario of fragmented 1D S = 1 AFM chains with a rather high defect concentration of about 17% and associated S = 1/2 edge states of the resulting finite Haldane chains.

Microwave-assisted hydrothermal synthesis was used to grow LiMnPO$_4$ micro- and nanocrystals from acetate precursors. By appropriate adjustment of the precursor concentration and the pH-value of the reactant, the product composition and purity along with the crystal size can be manipulated, resulting in particle-dimensions from around 10 mm down to a few 100 nm. Prisms and plates with hexagonal basal face as well as cuboid and rod-like particles were produced. The effects on the crystal morphology as well as on the materials texture and agglomeration tendency are discussed and a comprehensive agglomeration phase diagram is constructed.

We present a detailed $^7$Li- and $^{31}$P-NMR study on single crystalline LiMnPO$_4$ in the paramagnetic and antiferromagnetic phase (AFM, $T_N \sim$ 34 K). This allows us to determine the spin directions in the field-induced spin-flop phase. In addition, the anisotropic dipolar hyperfine coupling tensor of the $^7$Li- and $^{31}$P-nuclei is also fully determined by orientation and temperature dependent NMR experiments and compared to the calculated values from crystal structure data. Deviations of the experimental values from the theoretical ones are discussed in terms of Mn disorder which is induced by Li-disorder. In fact, the disorder in the Mn-sublattice is directly revealed by our diffuse x-ray scattering data. The present results provide experimental evidence for the Li-diffusion strongly coupling to structural distortions within the MnPO$_4$ host, which is expected to significantly affect the Li-mobility as well as the performance of batteries based on this material.

Ni-doped LiMn0.95Ni0.05PO4 single crystals have been grown for the first time by the travelling-solvent floating-zone method at low Argon pressure. The grown sample exhibits large single crystalline grains as revealed by means of polarization microscopy and X-ray Laue back scattering. The composition of the crystal was determined by Energy-dispersive X-ray spectroscopy. LiMn0.95Ni0.05PO4 orders in an orthorhombic olivine-like structure as expected and phase purity was confirmed by powder X-ray diffraction. An oriented cuboid with size of 2.4 x 2.5 x 2.7 mm3 along a, b, and c crystalline directions, respectively, was used for anisotropic magnetic measurements.

We have studied the structural and electronic phase diagrams of CeFeAsO1-xFx and SmFeAsO1-xFx by a detailed analysis of muon spin relaxation experiments, synchrotron X-ray diffraction, M\"ossbauer spectroscopy, electrical resistivity, specific heat, and magnetic susceptibility measurements (Full abstract in the main document).

We have studied the magnetodielectric and magnetoelastic coupling in TbFe3(BO3)4 single crystals by means of capacitance, magnetostriction and Raman spectroscopy measurements. The data reveal strong magnetic field effects on the dielectric constant and on the macroscopic sample length which are associated to long range magnetic ordering and a field-driven metamagnetic transition. We discuss the coupling of the dielectric, structural, and magnetic order parameters and attribute the origin of the magnetodielectric coupling to phonon mode shifts according to the Lyddane-Sachs-Teller (LST) relation., Comment: Accepted for publication in Physical Review B

The ability of bridging thiophenolate groups to transmit magnetic exchange interactions between paramagnetic Ni(II) ions has been examined. For this purpose, dinuclear and trinuclear Ni(II)-complexes were prepared and fully characterized by IR- and UV-vis spectroscopy, X-ray crystallography, static magnetization measurements and high-field electron spin resonance (HF-ESR). We compare structural and magnetic properties of the two Ni(II)-complexes and discuss the relationships between magnetic interactions and chemical bonding., Comment: 10 pages

Due to their extraordinary physical and chemical properties carbon nanotubes reveal a promising potential as biomedical agents for heating, temperature sensoring and drug delivery on the cellular level. Filling carbon nanotubes with tailored materials realises nanoscaled containers in which the active content is encapsulated by a protecting carbon shell. We describe different synthesis routes and show the structural and magnetic properties of carbon nanotubes. In particular, the filling with magnetic materials offers the potential for hyperthermia applications while the insertion of NMR active substances allows the usage as markers and sensors. The potential of carbon nanotubes for biomedical applications is highlighted by hyperthermia studies which prove their applicability for local in-situ heating. In addition we have shown that a non-invasive temperature control by virtue of a carbon-wrapped nanoscaled thermometer and filling with anti-cancer drugs is possible., Comment: Review

We have prepared the newly discovered Fe-based superconducting material $\rm LaO_{1-x}F_xFeAs$ ($0\leq x\leq 0.2$) in polycrystalline form and have investigated the samples by means of structural, thermodynamic and transport measurements. Our investigations reveal a non superconducting phase at $0\leq x\lesssim0.04$ which for $x=0$ is characterized by a structural transition towards an orthorhombic distortion at $T_s\approx 160$ K and antiferromagnetic spin order at $T_N\approx138$ K. Both transitions lead to strong anomalies in various transport properties as well as in magnetization and in specific heat. Remarkably, the transition temperatures are only weakly doping dependent up $x\lesssim 0.04$. However, the transitions are abruptly suppressed at $x\geq0.05$ in favour of a superconducting phase with a critical temperature $T_c\gtrsim 20$ K. Upon further increasing the F-doping $T_c$ increases up to a maximum of $T_c=26.8$ K at $x=0.1$ which is followed by a decrease down to $T_c\approx10$ K at $x\geq0.15$.