We aim to understand the relation between structure and properties of selected functional materials. For that, we work on developing synthesis and crystal growth routes, on chemical and structural characterization, and on investigating the physical properties of such materials. Relevant materials may comprise but are not limited to intermetallics, and pnictides. Properties of interest include high spin polarization, first order phase transitions, magnetic anisotropy, unconventional superconductivity, frustrated magnetism, strong spin-orbit coupling and nontrivial topology. Our pool of facilities includes different types of furnaces working in various atmospheres, thermal analysis, powder and Laue backscattering x-ray diffraction. For a complete list of our facilities, see here. We also use Nuclear Magnetic Resonance (55Mn and 59Co NMR) to study the local crystallographic, magnetic and electronic structure of ferromagnets in in bulk, thin film and nano-size form.
The interfacial Dzyaloshinskii-Moriya interaction (iDMI) is of great interest in thin-film magnetism because of its ability to stabilize chiral spin textures. Here, we utilize all-electrical propagating spin-wave spectroscopy to disentangle multiple contributions to spin wave frequency nonreciprocity to determine the iDMI by investigating nonreciprocities across a wide range of magnetic layer thicknesses (from 4 to 26 nm) in Pt/Co/Ir, Pt/Co/Pt, and Ir/Co/Pt stacks. We find the expected sign change in the iDMI when inverting the stack order and a negligible iDMI for the symmetric Pt/Co/Pt. We additionally extract a difference in surface anisotropies and find a large contribution due to the formation of different crystalline phases of the Co, which is corroborated using nuclear magnetic resonance and high-resolution transmission-electron-microscopy measurements. These insights will open up avenues to investigate, quantify, and disentangle the fundamental mechanisms governing the iDMI, and pave a way toward engineered large spin-wave nonreciprocities for magnonic applications.
We present a systematic study of the evolution of structural parameters and electronic correlations as a function of 3d band filling in a single crystal series of BaT2As2 (T = Cr–Cu). Our study finds a strong interplay between crystal structure, bonding behavior, band filling, and electronic properties.
Single crystals of iridates are usually grown by a flux method well above the boiling point of the SrCl2 solvent, hence, under non-equilibrium growth conditions. Here, we report the growth of Sr2IrO4, Sr3Ir2O7 and SrIrO3 single crystals in a reproducible way by using anhydrous SrCl2 flux well below its boiling point. Reducing the soak temperature below the solvent boiling point not only provides more stable and controllable growth conditions in contrast to previously reported growth protocols, but also extends considerably the lifetime of expensive platinum crucibles and reduces the corrosion of heating and thermoelements of standard furnaces, thereby reducing growth costs.
A new intermetallic ternary compound La6Pd2.28Sb15 was synthesized which crystallizes in the orthorhombic space group. The crystal structure contains a three-dimensional framework of Sb squares and ribbons that extend along the a axis, including complex Sb–Sb bonding. La6Pd2.28Sb15 is diamagnetic and metallic.
The structure-property relationship of Co2MnSi Heusler thin films upon the irradiation with He+ ions were studied using nuclear magnetic resonance (NMR) and transmission electron microscopy (TEM), and associated with the corresponding changes of the magnetic behavior.
We report on the synthesis of a series of Co2-xMnxB alloys and the investigation of their properties. Measurements of both, macroscopic and local magnetic properties, reveal an anomalous behavior as a function of manganese concentration.The good agreement between the advanced characterization and theory gives a deeper understanding of the Co2-xMnxB material system which can in the future be extended to other systems. Specifically, we find a complex magnetic coupling behavior between Mn atoms, which significantly affects the corresponding exchange interactions.
DFG "Magnetism, nematicity and superconductivity in 1111 oxypnictide single-crystals" with M. Braden, Universität zu Köln
We grow and characterize single crystals of oxides, sulfides and intermetallic materials exhibiting a variety of properties such as unconventional superconductivity, complex magnetism or ionic conduction. We use the crucible-free floating zone technique based on optical heating (including the operation of the 150 bars high-pressure image furnace), the Bridgman and the flux methods. Embedded within this group is the complex magnetic oxides junior research group led by Dr. R. Morrow specializing in double perovskites.
Leader of the Crystal Growth group: Dr. Andrey Maljuk
e-mail: firstname.lastname@example.org phone: +49 351 4659 633
Leader of the Double Perovskite group: Dr. Ryan C. Morrow
e-mail: email@example.com phone: +49 351 4659 228
|Olesia Voloshyna||Post-doc||crystal growth||+49 351 4659 801|
|Anastasiia Smerechuk||PhD student||double perovskite|
|Tamara Holub||PhD student||double perovskite|
|Robert Kluge||Technician||+49 351 4659 539|