Structural and magnetic properties of spin-1/2 layered ferrimagnet Bi2Cu5B4O14

• The new compound Bi2Cu5B4O14 is synthesized.
• It is found to be a spin-1/2 layered compound with repeating Cu-pentamer units.
• Structural and magnetic properties are investigated.
• Frustration arises due to completing antiferromagnetic and ferromagnetic interactions.
• It undergoes a ferrimagnetic ordering at TC = 25 K.

Polycrystalline sample of Bi2Cu5B4O14 was synthesized and its structural and magnetic properties were investigated by means of temperature dependent x-ray diffraction, magnetization, and heat capacity measurements. Bi2Cu5B4O14 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 θCW ≃ −39 K, suggesting the dominant ferromagnetic interaction between Cu2+ 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 TC ≃ 25 K. The modified Arrott analysis shows that Bi2Cu5B4O14 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 (γTα) with a reduced exponent (α ≃ 2.58). The change in magnetic entropy is calculated to be Smag ≃ 28 J/mol K at around 100 K which is close to the expected theoretical value of 28.81 J/mol K for Bi2Cu5B4O14.