Crystal growth and magnetic properties of atom K embedded in Na5Co15.5Te6O36

In this paper, we report the structural, magnetic and specific heat properties of a new compound Na _2.67K _1.33Pb _0.67Co _15.33Te ₆O ₃₆ (NKPCTO). The compound can be regarded as a new system charactered by the K and Pb atom embedded in the Kagome system Na ₅Co _15.5Te ₆O ₃₆ (NCTO). In the new structure, we find that the disordered occupations of the Na and Co(3) atoms is irrelevant to K atom site, and Pb has same site with K. The ground state is proposed to have an effective S = 1/2 due to the 3d ⁷ Co ²⁺ ion in octahedral coordination and considerable spin–orbit coupling. Magnetic and specific heat data uncover that only an antiferromagnetic phase transition develops in NKPCTO at 49 K. There are also ferromagnetic correlations above the Neel temperature, as well as anomalous hysteresis loops and multiple field-induced magnetic transitions at low temperatures.