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2. Magnetic properties of the solid solutions CePt1−xAuxAl (x = 0.1–0.9).

Author

Renner, Konstantin, Eustermann, Fabian, Niehaus, Oliver, and Janka, Oliver

Subjects
X-ray powder diffraction, MAGNETIC susceptibility, SOLID solutions, SPACE groups, CURIE temperature
Abstract

Members of the solid solutions CePt1–xAuxAl have been synthesized from the elements and pure samples could be obtained for the whole range of x from 0.1–0.9. Powder X-ray diffraction patterns indicated the TiNiSi-type structure (orthorhombic, space group Pnma) for the whole series, consistent with the end members CePtAl and CeAuAl. The lattice parameters and therefore also the unit cell volumes evolve in a linear fashion when going from CePtAl to CeAuAl. Magnetic susceptibility and magnetization investigations were performed for the compounds with x = 0.1, 0.2, 0.3, 0.5, 0.7 and 0.9. The results show that the ferromagnetic ground state of CePtAl gets destabilized for small degrees of substitution (x = 0.1) resulting in a lower Curie temperature. For larger values of x, changes towards an antiferromagnetic ground state are observed, in line with pure CeAuAl. [ABSTRACT FROM AUTHOR]

Published
2024
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4. Magnetic properties of the solid solutions CePt1−xAuxAl (x= 0.1–0.9)

Author

Renner, Konstantin, Eustermann, Fabian, Niehaus, Oliver, and Janka, Oliver

Abstract

Members of the solid solutions CePt1–xAuxAl have been synthesized from the elements and pure samples could be obtained for the whole range of xfrom 0.1–0.9. Powder X-ray diffraction patterns indicated the TiNiSi-type structure (orthorhombic, space group Pnma) for the whole series, consistent with the end members CePtAl and CeAuAl. The lattice parameters and therefore also the unit cell volumes evolve in a linear fashion when going from CePtAl to CeAuAl. Magnetic susceptibility and magnetization investigations were performed for the compounds with x= 0.1, 0.2, 0.3, 0.5, 0.7 and 0.9. The results show that the ferromagnetic ground state of CePtAl gets destabilized for small degrees of substitution (x= 0.1) resulting in a lower Curie temperature. For larger values of x, changes towards an antiferromagnetic ground state are observed, in line with pure CeAuAl.

Published
2024
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9. (Ca0.95Cd0.10)Pd2Cd3, SrPd2Cd3 and (Eu0.95Cd0.10)Pd2Cd3 with YNi2Al3 type structure – crystal chemistry and magnetic hyperfine interactions

Author

Johnscher, Michael, Gerke, Birgit, Kösters, Jutta, Block, Theresa, Niehaus, Oliver, Reimann, Maximilian Kai, and Pöttgen, Rainer

Subjects
HYPERFINE interactions, MAGNETIC crystals, EUROPIUM compounds, INTERMETALLIC compounds, MAGNETIC measurements
Abstract

The intermetallic compounds (Ca0.95Cd0.10)Pd2Cd3, SrPd2Cd3 and (Eu0.95Cd0.10)Pd2Cd3 were synthesized from the elements in sealed niobium ampoules in an induction furnace. The polycrystalline samples were characterized through their Guinier powder patterns. The structures were refined from single crystal X-ray diffractometer data: YNi2Al3 type, P6/mmm, a = 984.61(5), c = 455.33(3) pm, wR2 = 0.0216, 376 F2 values, 21 variables for (Ca0.95Cd0.10)Pd2Cd3, a = 998.55(8), c = 453.65(3) pm, wR2 = 0.0296, 341 F2 values, 17 variables for SrPd2Cd3 and a = 992.57(4), c = 457.34(2) pm, wR2 = 0.0300, 384 F2 values, 21 variables for (Eu0.95Cd0.10)Pd2Cd3. The striking crystal chemical motif in the three structures is a planar [PdCd2] Kagome-type layer. The two crystallographically independent Ca (Sr, Eu) atoms have a coordination number of 18 by 6 Pd and 12 Cd atoms. The calcium and europium compound show a small degree of Ca (Eu) substitution by Cd2 dumb-bells with 281 pm Cd–Cd in (Eu0.95Cd0.10)Pd2Cd3. Temperature dependent magnetic susceptibility measurements show Curie–Weiss behaviour (7.63(1) µB/Eu atom) for the europium compound and the onset of ferromagnetic ordering at TC = 14.9(2) K. The divalent character of europium is corroborated by 151Eu Mössbauer spectroscpy. [ABSTRACT FROM AUTHOR]

Published
2023
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19. Seizure of Z-Library Domain Detrimental to Student Access to Educational Materials

Author

Niehaus, Oliver

Subjects
Teaching -- Equipment and supplies, News, opinion and commentary, Sports and fitness
Abstract

Byline: Oliver Niehaus Seizure of Z-Library Domain Detrimental to Student Access to Educational Materials Oliver Niehaus|November 11, 2022 On Friday, Nov. 4, the Department of Justice and the FBI seized [...]

Published
2022

20. College Seemingly Abandons COVID Mitigation Efforts

Author

Niehaus, Oliver

Subjects
News, opinion and commentary, Sports and fitness
Abstract

Byline: Oliver Niehaus College Seemingly Abandons COVID Mitigation Efforts Oliver Niehaus|September 23, 2022 I started school at Oberlin last fall when there were signs all over campus that said, 'masks [...]

Published
2022

22. (Ca0.95Cd0.10)Pd2Cd3, SrPd2Cd3and (Eu0.95Cd0.10)Pd2Cd3with YNi2Al3type structure – crystal chemistry and magnetic hyperfine interactions

Author

Johnscher, Michael, Gerke, Birgit, Kösters, Jutta, Block, Theresa, Niehaus, Oliver, Reimann, Maximilian Kai, and Pöttgen, Rainer

Abstract

The intermetallic compounds (Ca0.95Cd0.10)Pd2Cd3, SrPd2Cd3and (Eu0.95Cd0.10)Pd2Cd3were synthesized from the elements in sealed niobium ampoules in an induction furnace. The polycrystalline samples were characterized through their Guinier powder patterns. The structures were refined from single crystal X-ray diffractometer data: YNi2Al3type, P6/mmm, a= 984.61(5), c= 455.33(3) pm, wR2 = 0.0216, 376 F2values, 21 variables for (Ca0.95Cd0.10)Pd2Cd3, a= 998.55(8), c= 453.65(3) pm, wR2 = 0.0296, 341 F2values, 17 variables for SrPd2Cd3and a= 992.57(4), c= 457.34(2) pm, wR2 = 0.0300, 384 F2values, 21 variables for (Eu0.95Cd0.10)Pd2Cd3. The striking crystal chemical motif in the three structures is a planar [PdCd2] Kagome-type layer. The two crystallographically independent Ca (Sr, Eu) atoms have a coordination number of 18 by 6 Pd and 12 Cd atoms. The calcium and europium compound show a small degree of Ca (Eu) substitution by Cd2dumb-bells with 281 pm Cd–Cd in (Eu0.95Cd0.10)Pd2Cd3. Temperature dependent magnetic susceptibility measurements show Curie–Weiss behaviour (7.63(1) µB/Eu atom) for the europium compound and the onset of ferromagnetic ordering at TC= 14.9(2) K. The divalent character of europium is corroborated by 151Eu Mössbauer spectroscpy.

Published
2023
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24. APd2Zn3 (A=Ca, Sr, Eu) with a CaCu5 superstructure.

Author

Gerke, Birgit, Niehaus, Oliver, Block, Theresa, Reimann, Maximilian Kai, and Pöttgen, Rainer

Subjects
*X-ray powder diffraction, *HYPERFINE coupling, *MAGNETIC susceptibility, *INTERMETALLIC compounds, *EUROPIUM, *SINGLE crystals
Abstract

The intermetallic phases APd2Zn3 (A=Ca, Sr, Eu) were synthesized from the elements in sealed niobium ampules in an induction furnace. The phase purity of the samples was checked by powder X‐ray diffraction (Guinier technique). The structures were refined from single crystal X‐ray diffractometer data: YNi2Al3 type (CaCu5 superstructure), P6/mmm, a=936.97(4), c=420.75(2) pm, wR2=0.0206, 259 F2 values, 17 variables for CaPd2Zn3, a=953.63(6), c=425.38(3) pm, wR2=0.0185, 230 F2 values, 17 variables for SrPd2Zn3 and a=948.20(7), c=423.20(3) pm, wR2=0.0209, 228 F2 values, 18 variables for EuPd2.12(1)Zn2.88(1). The europium‐based crystal showed a small homogeneity range through Pd/Zn mixing. The striking structural motifs of the APd2Zn3 phases are Kagome networks formed by the palladium and zinc atoms. The superstructure formation (discussed on the basis of a Bärnighausen tree) results from a different Pd/Zn coloring and a shift of one A position by c/2. The divalent character of europium in EuPd2Zn3 was substantiated by magnetic susceptibility and 151Eu Mössbauer spectroscopic measurements. EuPd2Zn3 orders ferrimagnetically at TC=17.5(5) K. The magnetization behavior at 3 K (two‐step magnetization) confirms the existence of two crystallographically independent europium sites. The 151Eu Mössbauer spectrum at 5 K shows full magnetic hyperfine field splitting (δ=−8.99(4) mm s−1 and BHf=27.7(1) T). [ABSTRACT FROM AUTHOR]

Published
2022
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25. Modulated ferromagnetic ordering and the magnetocaloric response of Eu4PdMg.

Author

Ryan, D. H., Legros, Anaëlle, Niehaus, Oliver, Pöttgen, Rainer, Cadogan, J. M., and Flacau, R.

Subjects
NEUTRONS, FERROMAGNETISM, FERROMAGNETIC resonance, MAGNETOCALORIC effects, THERMAL properties
Abstract

Neutron powder diffraction confirms that the primary ordering mode in Eu4PdMg is ferromagnetic with a europium moment of 6.5(2) μB. 151Eu Mössbauer spectroscopy shows that the unusual linear temperature dependence of the magnetisation reported for this system is an intrinsic property and not an artefact of the applied field. The form and temperature evolution of the 151Eu Mössbauer spectra strongly suggest that there is an incommensurate modulation to the magnetic structure that modifies the basic ferromagnetic order. This modulated structure may be the origin of the broad magnetocaloric response previously observed in Eu4PdMg. [ABSTRACT FROM AUTHOR]

Published
2015
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28. Antiferromagnetic ordering based on intermolecular London dispersion interactions in amphiphilic TEMPO ammonium salts

Author

Exner, Jessica, primary, Eusterwiemann, Steffen, additional, Janka, Oliver, additional, Doerenkamp, Carsten, additional, Massolle, Anja, additional, Niehaus, Oliver, additional, Daniliuc, Constantin G., additional, Pöttgen, Rainer, additional, Neugebauer, Johannes, additional, Studer, Armido, additional, and Eckert, Hellmut, additional

Published
2018
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29. Two superstructures of Ce3Rh4Ge4

Author

Voßwinkel, Daniel, primary, Hoffmann, Rolf-Dieter, additional, Svitlyk, Volodymyr, additional, Hermes, Wilfried, additional, Greiwe, Magnus, additional, Niehaus, Oliver, additional, Chevalier, Bernard, additional, Matar, Samir F., additional, Alam, Adel F. Al, additional, Nakhl, Michel, additional, Ouaini, Naïm, additional, and Pöttgen, Rainer, additional

Published
2017
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30. Molybdenum Oxide Nitrides of the Mo2(O,N,□)5 Type: On the Way to Mo2O5

Author

Weber, Dominik, primary, Huber, Manop, additional, Gorelik, Tatiana E., additional, Abakumov, Artem M., additional, Becker, Nils, additional, Niehaus, Oliver, additional, Schwickert, Christian, additional, Culver, Sean P., additional, Boysen, Hans, additional, Senyshyn, Anatoliy, additional, Pöttgen, Rainer, additional, Dronskowski, Richard, additional, Ressler, Thorsten, additional, Kolb, Ute, additional, and Lerch, Martin, additional

Published
2017
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31. Cooperative Magnetism in Crystalline N -Aryl-Substituted Verdazyl Radicals: First-Principles Predictions and Experimental Results

Author

Eusterwiemann, Steffen, primary, Dresselhaus, Thomas, additional, Doerenkamp, Carsten, additional, Janka, Oliver, additional, Niehaus, Oliver, additional, Massolle, Anja, additional, Daniliuc, Constantin G., additional, Eckert, Hellmut, additional, Pöttgen, Rainer, additional, Neugebauer, Johannes, additional, and Studer, Armido, additional

Published
2017
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32. Synthesis and Characterization of the High-Pressure Nickel Borate γ-NiB4O7

Author

Schmitt, Martin K., primary, Janka, Oliver, additional, Niehaus, Oliver, additional, Dresselhaus, Thomas, additional, Pöttgen, Rainer, additional, Pielnhofer, Florian, additional, Weihrich, Richard, additional, Krzhizhanovskaya, Maria, additional, Filatov, Stanislav, additional, Bubnova, Rimma, additional, Bayarjargal, Lkhamsuren, additional, Winkler, Björn, additional, Glaum, Robert, additional, and Huppertz, Hubert, additional

Published
2017
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33. The gallium intermetallics REPdGa3 (RE = La, Ce, Pr, Nd, Sm, Eu) with SrPdGa3-type structure

Author

Seidel, Stefan, Niehaus, Oliver, Matar, Samir F., Janka, Oliver, Gerke, Birgit, Rodewald, Ute Ch., Pöttgen, Rainer, Institut für Anorganische und Analytische Chemie, Westfälische Wilhelms-Universität Münster (WWU), Institut de Chimie de la Matière Condensée de Bordeaux (ICMCB), Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut Polytechnique de Bordeaux-Université de Bordeaux (UB), Deutsche Forschungsgemeinschaft through SPP 1458 Hochtemperatursupraleitung, and Fonds der Chemischen Industrie and the NRW Forschungsschule Molecules and Materials

Subjects
[CHIM.MATE]Chemical Sciences/Material chemistry
Abstract

International audience; The gallium-rich intermetallic phases REPdGa3 (RE = La, Ce, Pr, Nd, Sm, Eu) were obtained by arc-melting of the elements and subsequent annealing for crystal growth. The samples were studied by X-ray diffraction on powders and single crystals. The structures of three crystals were refined from X-ray diffractometer data: SrPdGa3 type, Cmcm, a = 634.3(1), b = 1027.2(1), c = 593.5(1) pm, wR = 0.0621, 380 F2 values, 20 variables for CePd0.80(4)Ga3.20(4), a = 635.9(1), b = 1027.5(1), c = 592.0(1) pm, wR = 0.1035, 457 F2 values, 19 variables for CePdGa3, and a = 640.7(1), b = 1038.2(1), c = 593.7(1) pm, wR = 0.0854, 489 F2 values, 19 variables for EuPdGa3. The REPdGa3 gallides are orthorhombic superstructure variants of the aristotype ThCr2Si2. The palladium and gallium atoms build up polyanionic [PdGa3]δ− networks with Pd–Ga and Ga–Ga distances of 248–254 and 266–297pm, respectively, in EuPdGa3. The rare earth atoms fill cavities within the polyanionic networks. They are coordinated by five palladium and twelve gallium atoms. Taking CePdGa3 as an illustrative representative, the band structure calculations show largely dispersive itinerant s, p bands and little dispersive d (Pd) and f (Ce) bands, the latter crossing the Fermi level at large magnitude leading to magnetic instability in a spin-degenerate state and a subsequent antiferromagnetic ground state with a small moment of ±0.36 μB on Ce. The bonding characteristics indicate a prevailing Ce–Ga bonding versus Pd–Ga and Ce–Pd. Temperature-dependent magnetic susceptibility and 151Eu Mössbauer spectroscopic measurements point to stable trivalent lanthanum, cerium, praseodymium, and neodymium, but divalent europium. SmPdGa3 shows intermediate valence. Antiferromagnetic ordering occurs at TN = 5.1(5), 7.0(5), 6.3(5), 11.9(5), and 23.0(5) for RE = Ce, Pr, Nd, Sm, and Eu, respectively.

Published
2014

47. A ZrNiAl related high-pressure modification of CeRuSn

Author

Niehaus, Oliver, primary, Heymann, Gunter, additional, Huppertz, Hubert, additional, Rodewald, Ute Ch., additional, Chevalier, Bernard, additional, Matar, Samir F., additional, Hoffmann, Rolf-Dieter, additional, and Pöttgen, Rainer, additional

Published
2016
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