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تسجيل مستخدم جديدBulk antiferromagnetism in $bf Na_{0.82}CoO_2$ single crystals
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Susceptibility, specific heat, and muon spin rotation measurements on high-quality single crystals of $rm Na_{0.82}CoO_2$ have revealed bulk antiferromagnetism with N{e}el temperature $rm T_N = 19.8 pm 0.1$ K and an ordered moment perpendicular to the $rm CoO_2$ layers. The magnetic order encompasses nearly 100% of the crystal volume. The susceptibility exhibits a broad peak around 30 K, characteristic of two-dimensional antiferromagnetic fluctuations. The in-plane resistivity is metallic at high temperatures and exhibits a minimum at $rm T_N$.
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The magnetic and transport properties are systematically studied on the single crystal $Na_{0.55}CoO_2$ with charge ordering and divergency in resistivity below 50 K. A long-range ferromagnetic ordering is observed in susceptibility below 20 K with t
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unequivocal $^{59}$Co NMR evidence that below $T_{CO}sim51 K$, the insulating ground state of the itinerant antiferromagnet Na$_{0.5}$CoO$_{2}$ ($T_{N}sim 86 K$) is induced by charge ordering.
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Compounds based on the Fe2P structure have continued to attract interest because of the interplay between itinerant and localized magnetism in a non-centrosymmetric crystal structure, and because of the recent developments of these materials for magn
etocaloric applications. Here we report the growth and characterization of mm size single crystals of FeMnP0.8Si0.2. Single crystal x-ray diffraction, magnetization, resistivity, Hall and heat capacity data are reported. Surprisingly, the crystals exhibit itinerant antiferromagnetic order below 158 K with no hint of ferromagnetic behavior in the magnetization curves and with the spins ordered primarily in the ab plane. The room temperature resistivity is close to the Ioffe-Regel limit for a metal. Single crystal x-ray diffraction indicates a strong preference for Mn to occupy the larger pyramidal 3g site. The cation site preference in the as-grown crystals and the antiferromagnetism are not changed after high temperature anneals and a rapid quench to room temperature.
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