Crystal Growth of Spin Chain Compound Sr₂CuO₃ Doped with Quantum Defects: Zn, Co, Ni, and Mn

Abstract

Single crystals of spin chain compound Sr 2 CuO 3 and its doped variants consisting of Zn (1%), Co (1 and 2.5%), Ni (1 and 10%), and Mn (0.25%) at the Cu site were grown using the traveling solvent floating zone method. The floating zone at the end of each growth experiment was analyzed in detail to investigate the melt composition, the shape of the crystal–melt interface, the region of the feed adjacent to the melt, and the dopant concentration of the melt. The composition of the molten zone was found to be in good agreement with the peritectic point associated with the incongruent decomposition of Sr 2 CuO 3 . The floating zones in each case were found to be extended deeply into the feed where its composition varied in accordance with the binary SrO–CuO phase diagram. Analysis of the dopant concentration revealed significant accumulation of Zn and Co in the floating zones, suggesting that the actual Zn/Co concentration in the grown crystals is less than the nominal value. No such accumulation was observed with Ni and Mn doping. Magnetic susceptibility of all the grown crystals was measured under two field orientations: parallel and perpendicular to the chains. We show that upon inclusion of a quantum defect in a spin 1/2 chain the magnetic ground state evolves in a manner that is characteristic of the quantum defect.