Crystal growth and thermodynamic properties of (Ca, La) ₁₄Cu₂₄O₄₁

High quality, centimeter size single crystals of Ca_14-xLa_xCu₂₄O₄₁ have been successfully grown using the travelling solvent floating zone (TSFZ) method in association with an image furnace. Crystals grown under oxygen pressures up to 13 bar are single phase for 2 ≤ x ≤ 5. Growth initiated on a single crystalline seed, in combination with an appropriate solvent disk, yields a single domain almost directly from the beginning of the growth. Crystals were characterized by EDX, TGA and X-ray powder diffraction. In addition magnetic susceptibility and specific heat measurements were performed. Long range antiferromagnetic order occurs at T_N=9.7 K for x_La = 5, whereas for lower La concentrations T_N is considerably suppressed.