Browsing by Author "Czerwinski, KR"

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    Magneto-structural coupling in SrTcxRu1-xO3 (x = 0.25,0.5) perovskites
    (Elsevier, 2020-07) Reynolds, E; Romao, CP; Brand, HEA; Thorogood, GJ; Poineau, F; Czerwinski, KR; Kennedy, BJ
    The structure and magnetic properties of the mixed technetium-ruthenium perovskites SrTcxRu1-xO3 (x ​= ​0.25 and 0.5) have been investigated using variable temperature synchrotron X-ray diffraction, magnetic susceptibility measurements, and DFT calculations. Both oxides are isostructural with SrRuO3 and SrTcO3, and there is no evidence of long-range cation order. Magnetostriction is observed along the c-axis for both oxides. The inverse susceptibility and DFT calculations suggest a cation-disordered ferrimagnetic ground state for SrTc 0.5 Ru 0.5 O3. ©2020 Elsevier Inc.
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    Structure and magnetism in Sr A_xTcO 3 perovskites: importance of the A-site cation
    (American Physical Society, 2017-02-27) Reynolds, EM; Avdeev, M; Thorogood, GJ; Poineau, F; Czerwinski, KR; Kimpton, JA; Yu, M; Kayser, P; Kennedy, BJ
    The Sr1−xBaxTcO3 (x=0, 0.1, 0.2) oxides were prepared and their solid-state and magnetic structure studied as a function of temperature by x-ray and neutron powder diffraction. The refined Tc moments at room temperature and Néel temperatures for Ba0.1Sr0.9TcO3 and Ba0.2Sr0.8TcO3 were 2.32(14)μβ and 2.11(13)μβ and 714∘C and 702∘C, respectively. In contrast to expectations, the Néel temperature in the series Sr1−xAxTcO3 decreases with increasing Ba content. This observation is consistent with previous experimental measurements for the two series AMO3 (M=Ru, Mn; A=Ca, Sr, Ba) where the maximum magnetic ordering temperature was observed for A=Sr. Taken with these previous results the current work demonstrates the critical role of the A-site cation in the broadening of the π∗ bandwidth and ultimately the magnetic ordering temperature.©2017 American Physical Society
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    Thermal expansion behavior in TcO2. Toward breaking the Tc–Tc bond
    (American Chemical Society, 2017-07-24) Reynolds, EM; Zhang, Z; Avdeev, M; Thorogood, GJ; Poineau, F; Czerwinski, KR; Kimpton, JA; Kennedy, BJ
    The structure of TcO2 between 25 and 1000 °C has been determined in situ using X-ray powder diffraction methods and is found to remain monoclinic in space group P21/c. Thermal expansion in TcO2 is highly anisotropic, with negative thermal expansion of the b axis observed above 700 °C. This is the result of an anomalous expansion along the a axis that is a consequence of weakening of the Tc–Tc bonds. © 2017 American Chemical Society