Solid State Chemistry Group
at the Laboratory for Multiscale materials eXperiments
We are working on the synthesis and characterization of ceramic and single crystal materials with novel electronic and magnetic properties. Numerous complex oxide materials have been successfully crystallized by the Traveling Solvent Floating Zone (TSFZ) method using an optical furnace. This includes cuprates, manganates, orthoferrites, cobaltites, borates and phosphates. Novel chalcogenide iron superconductors have been synthesized as powders and single crystals (Bridgman method). read more
Doctoral thesis award of the Dr. Alfons Paulus Foundation at the University of Regensburg, Faculty of Chemistry and Pharmacy for Igor Plokhikh
On 14th of July 2022 Dr Igor Plokhikh (currently postdoc at SSCG, LMX PSI) has been awarded with the Doctoral thesis award of the Dr. Alfons Paulus Foundation at the University of Regensburg, Faculty of Chemistry and Pharmacy. He completed his doctoral studies at the group of Prof. Arno Pfitzner working on synthesis, crystal growth and characterization of crystal and magnetic structures of new magnetic Eu2+-containing compounds. This work resulted in discovery of over 10 new compounds, some of which exhibit complex magnetic phase diagrams.
First-ever rare earth nickelate single crystals lead to first experimental evidence supporting predicted multiferroicity
Due to the Corona pandemic starting 1. May 2021, new access rules to the SSC user facilites will apply. More details can be found at https://www.psi.ch/de/lmx-ssc/access-rules.
On 31.05.2019, Fei Li passed successfully his PhD defence at the ETH Materials Department. The title of his thesis is "Crystal and Magnetic Structure of R1/3Sr2/3FeO3 (R = La,Pr,Nd)”
Dr Pascal Puphal (currently a Postdoc at PSI, LMX, Solid State Chemistry Group) has recently been awarded with the DGKK young researcher price from the German Crystal Growth Community on his Ph.D. work performed in the group of Cornelius Krellner at the Geothe University Frankfurt am Main on the topic "Tuning two dimensional Cu-based quantum spin systems". The work covers the stabilization and proof of a 2D dimer structure by Sr substitution in Han Purple and the research of novel kagome materials of the prominent quantum spin liquid candidate herbertsmithite by the hydrothermal route.
In high-temperature cuprate superconductors, stripe order refers broadly to a coupled spin and charge modulation with a commensuration of eight and four lattice units, respectively. How this stripe order evolves across optimal doping remains a controversial question. Here we present a systematic resonant inelastic x-ray scattering study of weak charge correlations in La2−xSrxCuO4 and La1.8−xEu0.2SrxCuO4. Ultra high energy resolution experiments demonstrate the importance of the separation of inelastic and elastic scattering processes. Long-range temperature-dependent stripe order is only found below optimal doping. At higher doping, short-range temperature-independent correlations are present up to the highest doping measured. This transformation is distinct from and preempts the pseudogap critical doping. We argue that the doping and temperature-independent short-range correlations originate from unresolved electron–phonon coupling that broadly peaks at the stripe ordering vector. In La2−xSrxCuO4, long-range static stripe order vanishes around optimal doping and we discuss both quantum critical and crossover scenarios.
From new neutron powder diffraction experiments on the chiral cubic (P213) magnet manganese germanide (MnGe), we analyze all of the possible crystal symmetry-allowed magnetic superstructures that are determined successfully from the data. The incommensurate propagation vectors k of the magnetic structure are found to be aligned with the  cubic axes, and correspond to a magnetic periodicity of about 30 Å at 1.8 K. Several maximal crystallographic symmetry magnetic structures are found to fit the data equally well and are presented. These include topologically nontrivial magnetic hedgehog and “skyrmion” structures in multi-k cubic or orthorhombic 3+3 and orthorhombic 3+2 dimensional magnetic superspace groups respectively, with either potentially responsible for topological Hall effect. The presence of orthorhombic distortions in the space group P212121 caused by the transition to the magnetically ordered state does not favor the cubic magnetic hedgehog structure, and leave both orthorhombic hedgehog and skyrmion models as equal candidates for the magnetic structures. We also report on a combined mechanochemical and solid-state chemical route to synthesize MnGe at ambient pressures and moderate temperatures, and compare with samples obtained by the traditional high pressure synthesis.
We present magnetization and neutron powder diffraction studies in the temperature range 2K to 300K for oxygen stoichiometric R1/3Sr2/3FeO (R = Pr and Nd). From full symmetry analysis, we proposed two magnetic models by a combined application of irreducible representations and magnetic space groups. Both models fit equally well the neutron powder diffraction data.
GdSb0.46Te1.48, a nonsymmorphic Dirac semimetal with Dirac nodes at the Fermi level, has a rich magnetic phase diagram with one of the phases predicted to be an antiferromagnetic skyrmion state. In the current work, we investigate GdSb0.71Te1.22 through bulk magnetization measurements, single-crystal, and powder synchrotron X-ray diffraction, as well as single-crystal hot-neutron diffraction. We resolve a weak orthorhombic distortion with respect to the tetragonal structure and charge density wave (CDW) satellites due to incommensurate modulations of the crystal structure. At 2 K the magnetic structure is modulated with two propagation vectors, kI = (0.45 0 0.45) and kII = (0.4 0 0), with all their arms visible. While kI persists up to the transition to the paramagnetic state at TN = 11.9 K, kII disappears above an intermediate magnetic transition at T1 = 5 K. Whereas magnetic field applied along the c-axis has only a weak effect on the intensity of antiferromagnetic reflections, it is effective in inducing an additional ferromagnetic component on Gd atoms. We refine possible magnetic structures of GdSb0.71Te1.22 and discuss the possibility of hosting magnetic textures with non-trivial 3D+ 2 topologies in the GdSb1−xTe1+x series.
Crossover of high-energy spin fluctuations from collective triplons to localized magnetic excitations in Sr14−xCaxCu24O41 ladder
We studied the magnetic excitations in the quasi-one-dimensional (q-1D) ladder subsystem of Sr14−xCaxCu24O41 (SCCO) using Cu L3-edge resonant inelastic X-ray scattering (RIXS). By comparing momentum-resolved RIXS spectra with high (x = 12.2) and without (x = 0) Ca content, we track the evolution of the magnetic excitations from collective two-triplon (2 T) excitations (x = 0) to weakly- dispersive gapped modes at an energy of 280 meV (x = 12.2)...