Synthesis and Crystal Growth Research Team

Intermetallic Magnetic Materials Group

Head: Dr. S. Wurmehl

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Crystal Growth Group

Head: Dr. A. Maljuk

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Intermetallic Magnetic Materials Group

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 functional material. 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 and temperatur regimes, 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.

Head of Department/Group Leader: Dr. Sabine Wurmehl

Room D2E.13     Phone: +49 351 4659 519       Email

Selected publications

ScAuIn – A new representative of the RAuIn series

V.V. Romaka, L. Amigo, D. Franco, L.T. Corredor, S. Wurmehl, B. Büchner, S. Seiro J. Solid State Chem. 314, 123416 (2022)

A new representative of the RAuIn series was discovered in the Sc-Au-In system. ScAuIn crystallizes in the hexagonal HfRhSn-type structure (space group P-62c) with a ​= ​0.75667(2), c ​= ​0.71873(2) nm). Magnetization measurements revealed that ScAuIn is a Pauli paramagnet with magnetic susceptibility of ∼6 ​× ​10−5 emu/mol. The Sommerfeld coefficient γ of 2.8 ​mJ ​K−2 ​mol−1 derived from the specific heat measurements is comparable with those obtained from the modeled density of states at the Fermi level N(EF). Ab initio calculations predict metallic conductivity and show strong chemical bonding within the [InAu] sublattice. The structural stability of the RAuIn with ZrNiAl and HfRhSn structure types is discussed based on crystal chemistry analysis and DFT modeling.

FeMn3Ge2Sn7O16: A Perfectly Isotropic 2-D Kagomé Lattice that Breaks Magnetic Symmetry with Partial Spin Order

M. C. Allison, S. Wurmehl, B. Büchner, J.  L. Vella, T. Söhnel, S. A. Bräuninger, H.-H. Klauss, M. Avdeev, F. P. Marlton, S. Schmid, C. D. Ling

Chem. Mater. 34, 1369 (2022)

FeMn3Ge2Sn7O16 is a fully ordered stoichiometric phase containing an undistorted hexagonal kagomé lattice of Mn2+ cations. It represents not only an important expansion of the chemistry of the complex composite FeFe3Si2Sn7O16 structure type, by replacing silicon with germanium, but also an improvement on the perfection of the kagomé lattice by replacing anisotropic high-spin Fe2+ (d6, L = 2) with isotropic high-spin Mn2+ (d5, L = 0), controlled by the size-matched replacement of SiO44– with GeO44– bridging units. This anisotropy was suspected of playing a role in the unique “striped” magnetic structure of FeFe3Si2Sn7O16 at low temperatures, which breaks hexagonal symmetry and leaves one-third of the magnetic moments geometrically frustrated and fluctuating down to at least 0.1 K. We observe the same striped magnetic structure in FeMn3Ge2Sn7O16, ruling out single-ion anisotropy as the driving force and deepening the intrigue around the apparent “partial spin-liquid” nature of these compounds.

Evolution of Structure and Electronic Correlations in a Series of BaT2As2 (T = Cr–Cu) Single Crystals

S. Selter, et al., Inorg. Chem. 59, 16913 (2020)

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.

Flux growth of Srn+1IrnO3n+1 (n=1, 2, infinity) crystals

K. Manna, et al., J. Cryst. Growth 540, 125657 (2020)

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.

Current projects

DFG "Magnetism, nematicity and superconductivity in 1111 oxypnictide single-crystals" with M. Braden, Universität zu Köln(PL Wurmehl)

SFB 1143:  Correlated Magnetism: From Frustration To Topology - Synthesis, crystal growth, and phase diagrams of frustrated magnets (B01) (with Dr. Anna Wolter-Giraud, IFW; PL Wurmehl)

Integrated Research Training Group (MGK) as part of SFB 1143 (PL Wurmehl)

Completed projects

DFG "Exploring the Nuclear Magnetic Resonance (NMR) technique as tool for modern materials research"(PL Wurmehl)

BMBF UKRATOP "Topological order of electrons in solids:  New materials, Phenomena &  Application Concepts"

BMBF -ERA-RUS-NET "New Layered Intermetallic Iron-based Superconductors and Related Compounds" (coordinated by PL Wurmehl)

DFG "Rationale Synthese neuartiger niedrigdimensionaler Materialien durch Abstimmung des Fermi-Niveaus durch chemische Dotierung" (PL Sturza)

DFG-materials world network "Halbmetallischer Transport in chemisch komplexen Systemen" (with P. Woodward and F.Y. Yang, both OSU, Ohio, USA; PL Wurmehl)

DFG "Tetragonal distorted Mn3-xGa Heusler compounds: Novel hardmagnetic materials without 4f electrons" (PL Wurmehl)

DFG "Synthesis and crystal growth of new and well-established iron pnictide superconductors" (PL Wurmehl)

DFG  "GRK 1621:  Itinerant Magnetism and Superconductivity in Intermetallic Compounds" (Wurmehl as participating researcher)

DFG_Emmy- Noether-Project "Optimierte Heusler Verbindungen für die Spintronik durch Kontrolle der Struktur-Eigenschaftsbeziehungen" (PL Wurmehl)

DFG "NMR als Methode zur strukturellen Charakterisierung sowie zur Messung der Spinpolarisation halbmetallischer Ferromagnete" (PL Wurmehl, research stay at TU Eindhoven)




Felix Anger

Patrizia Fritsch

Vakula Hlushko

Dr. Myroslava Horiacha

Gloria Kirste

Robin Kramer

Dr. Wolfgang Löser

Dr. Vitaliy Romaka

Dr. Sabine Wurmehl, see personal wepbpage


Christian Blum

Chika Schlage

Rowena Wachtel


Former research scientists

Dr. A. Alfonsov

Dr. M. Allison,

Dr. M. Belesi

Dr. T. Dey

 Dr. F. Hammerath

Dr. L. Harnagea

Dr. S. Khim

Dr. K. Manna,

 Dr. S. Singh

Dr. I. Sturza

Former PhD students

Dr. Claudia Nacke

Dr. Saicharan Aswartham

Dr. Steven Rodan

Dr. Ahmad Omar

Dr. Markus Gellesch

Dr. Rhea Kappenberger

Former Diploma/Master students 

Y. Hacisalohoglu

S. Marx

F. Naumann

F. Seifert

M. Schulze

H. Stummer

Former students 

M. Brandt

D. Hettmann                                                               

S. Storch

I. Vicon

R. Zaunick

A. Zimmermann

Crystal Growth Group

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:                     phone:  +49 351 4659 633


Leader of the Double Perovskite group:           Dr. Ryan C. Morrow

e-mail:                 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


Laser-assisted floating zone growth of BaFe2S3 large-sized ferromagnetic- impurity-free single crystals,  M.L.Amigó, A.Maljuk, K.Manna, Q.Stahl, C.Felser, C.Hess, A.U.B.Wolter, J.Geck, S.Seiro, B.Büchner, Crystals 11, 758 (2021).

TSFZ growth of Nd-substituted LSCO superconducting crystals, O.Voloshyna, K.Karmakar, A.Maljuk, V.V.Romaka, C.G.F. Blum, S.Seiro, B.Büchner, J.Crystal Growth 562, 126082 (2021)

Flux growth of Srn+1IrnO3n+1 (n = 1, 2, ∞), K. Manna, G. Aslan-Cansever, A. Maljuk, S. Wurmehl, S. Seiro, and B. Büchner, J. Crystal Growth 540, 125657 (2020)

Charge transfer energy in iridates: a hard x-ray photoelectron spectroscopy study, D. Takegami, D. Kasinathan, K. K. Wolff, S. G. Altendorf, C.-F. Chang, K. Hoefer, A. Meléndez-Sans, Y. Utsumi, F. Meneghin, T. D. Ha, C.-H. Yen, K. Chen, C.-Y Kuo, Y. F. Liao, K.-D. Tsuei, R. Morrow, S. Wurmehl, B Büchner, B. E. Prasad, M. Jansen, A. C. Komarek, P. Hansmann, L. H. Tjeng, Phys. Rev. B 102, 045119 (2020).

Discovery, Crystal Growth, and Characterization of Garnet Eu2PbSb2Zn3O12, R. Morrow, M. I. Sturza, R. Ray, C. Himcinschi, J. Kern, P. Schlender, S. Wurmehl, B. Büchner, Eur. J. Inorg. Chem. 26, 2512-2520 (2020).

Complex magnetic properties in the mixed 4f−5d double perovskite iridates X2ZnIrO6 (X = Nd, Sm, Eu, Gd), M. Vogl, R. Morrow, A. A. Aczel, R. Beltran Rodriguez, A. U. B. Wolter, S. Wurmehl, S. Aswartham, B. Büchner, Phys. Rev. Materials 4, 054413 (2020).

Laser-diode-heated floating-zone crystal growth of ErVO3, P. Telang, A. Maljuk, D. Rout, R. Hu, M. Skoulatos, K. Karmakar, S. Seiro, B. Roessli, U. Stuhr, B. Büchner, S.-W. Cheong and S. Sing, J. Crystal Growth 507, 406 (2019)

Bichalcogenide Model Systems for Magnetic Chains with Variable Spin Sizes and Optional Crystallographic InversionSymmetry, M. Valldor, R. Morrow, Inorg. Chem. 58 (18), 11978-11982 (2019). [Invited forum paper]

Growth of LiCoO2 single crystals by the TSFZ method,  S.Nakamura, A.Maljuk, Y.Maruyama, M. Nagao, S.Watauchi, T. Hayashi, Y.Anzai, Y.Furukawa, C.D. Ling, G.Deng, M.Avdeev, B.Büchner, I.Tanaka, Crystal Growth and Design 19,  415 (2019)