Pb2MnTeO6 Double Perovskite: An Antipolar Anti-ferromagnet

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• 作者：Maria Retuerto ; Stella Skiadopoulou ; Man-Rong Li ; Artem M. Abakumov ; Mark. Croft ; Alexander Ignatov ; Tapati Sarkar ; Brian M. Abbett ; Jan Pokorný ; Maxim Savinov ; Dmitry Nuzhnyy ; Jan Prokleška ; Milinda Abeykoon ; Peter W Stephens ; Jason P. Hodges ; Přemysl Vaněk ; Craig J. Fennie ; Karin M. Rabe ; Stanislav Kamba ; Martha Greenblatt
• 刊名：Inorganic Chemistry
• 出版年：2016
• 出版时间：May 2, 2016
• 年：2016
• 卷：55
• 期：9
• 页码：4320-4329
• 全文大小：667K
• 年卷期：0
• ISSN：1520-510X

文摘

Pb₂MnTeO₆, a new double perovskite, was synthesized. Its crystal structure was determined by synchrotron X-ray and powder neutron diffraction. Pb₂MnTeO₆ is monoclinic (I2/m) at room temperature with a regular arrangement of all the cations in their polyhedra. However, when the temperature is lowered to ∼120 K it undergoes a phase transition from I2/m to C2/c structure. This transition is accompanied by a displacement of the Pb atoms from the center of their polyhedra due to the 6s² lone-pair electrons, together with a surprising off-centering of Mn²⁺ (d⁵) magnetic cations. This strong first-order phase transition is also evidenced by specific heat, dielectric, Raman, and infrared spectroscopy measurements. The magnetic characterizations indicate an anti-ferromagnetic (AFM) order below T_N ≈ 20 K; analysis of powder neutron diffraction data confirms the magnetic structure with propagation vector k = (0 1 0) and collinear AFM spins. The observed jump in dielectric permittivity near ∼150 K implies possible anti-ferroelectric behavior; however, the absence of switching suggests that Pb₂MnTeO₆ can only be antipolar. First-principle calculations confirmed that the crystal and magnetic structures determined are locally stable and that anti-ferroelectric switching is unlikely to be observed in Pb₂MnTeO₆.