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Carbon-substituted MgB2 single crystals

Sergey Lee·Takahiko Masui·Ayako Yamamoto·Hiroshi Uchiyama·Setsuko Tajima
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Abstract

Carbon-substituted MgB2 single crystals, Mg(B_1-xC_x)_2 of 0.3-1.0 mm size were grown for x=0.02-0.15 by a high-pressure technique. The doping dependence of lattice constants studied in a range of x=0.0-0.2 shows a monotonic decrease in a, while the c parameter remains almost invariant. Using X-ray diffraction and Auger electron spectroscopy, the solubility limit of C in MgB2 was estimated to be about 15(+/-)1%,which is substantially larger than that reported for the polycrystalline samples synthesized by encapsulation techniques. Measurements of temperature dependence of magnetization and resistivity showed a dramatic decrease in Tc with C-substitution, followed by complete suppression of superconductivity for x>0.125. Resistivity measurements in magnetic fields parallel and perpendicular to the basal plane of the crystals showed a nearly isotropic state in the heavily-doped crystals (x>0.1).

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Sergey Lee, Takahiko Masui, Ayako Yamamoto, Hiroshi Uchiyama, Setsuko Tajima. 2003-05-21. Carbon-substituted MgB2 single crystals. https://doi.org/10.1016/s0921-4534(03)01296-6

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