ChemInform Abstract: Structural and Magnetic Properties of Spin-1/2 Layered Ferrimagnet Bi2Cu5B4O14

Polycrystalline sample of Bi 2 Cu 5 B 4 O 14 was synthesized and its structural and magnetic properties were investigated by means of temperature dependent x-ray diffraction, magnetization, and heat capacity measurements. Bi 2 Cu 5 B 4 O 14 is found to be a spin-1/2 layered compound with repeating Cu-pentamer units. DC magnetic susceptibility at high temperatures follows the Curie-Weiss law with a large and negative Curie-Weiss temperature θ CW ≃ −39 K, suggesting the dominant ferromagnetic interaction between Cu 2+ ions. A positive curvature in inverse susceptibility and a magnetization hysteresis with reduced ordered moment at T = 2.1 K pinpoint the ferrimagnetic nature of the compound with T C ≃ 25 K. The modified Arrott analysis shows that Bi 2 Cu 5 B 4 O 14 is a good example of Heisenberg ( β = 0.367 and γ = 1.388) ferrimagnet. Heat capacity data at low temperatures (i.e. in the ordered state) follows a power law ( γT α ) with a reduced exponent ( α ≃ 2.58). The change in magnetic entropy is calculated to be S mag ≃ 28 J/mol K at around 100 K which is close to the expected theoretical value of 28.81 J/mol K for Bi 2 Cu 5 B 4 O 14 .