Crystal Structures and Low-Dimensional Ferromagnetism of Sodium Nickel Phosphates Na5Ni2(PO4)3·H2O and Na6Ni2(PO4)3OHстатья
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Дата последнего поиска статьи во внешних источниках: 21 февраля 2019 г.
Аннотация:Two new sodium nickel phosphates, Na5Ni2(PO4)3·H2O (I) and Na6Ni2(PO4)3OH (II), have been synthesized hydrothermally and characterized by synchrotron X-ray diffraction, electron diffraction, low-temperature thermodynamic and magnetic measurements, and ab initio calculations. Unlike the majority of Ni2+ compounds, I and II show predominant ferromagnetic exchange couplings. I crystallizes in the monoclinic space group P21/n (a = 14.0395(4) Å, b = 5.1847(14) Å, c = 16.4739(4) Å, β = 110.4186(14)°) and features chains of ferromagnetically coupled Ni2+ ions. In II with the orthorhombic space group Pcmb (a = 7.5007(15) Å, b = 21.4661(4) Å, c = 7.1732(15) Å), the ferromagnetically coupled Ni2+ ions form dimers arranged on a spin ladder. Both compounds represent rare examples of quasi-one-dimensional ferromagnets. Structural features behind this unusual magnetic behavior are discussed.