Antiferromagnetism in the semiconducting lanthanide cuprates Ln2CuO4

The semiconducting lanthanide cuprates Pr₂CuO₄, Nd₂CuO₄, and Gd₂CuO₄ have been investigated using X-ray diffraction, magnetic susceptibility, and electron paramagnetic resonance techniques. The susceptibility and resonance studies indicate that the Cu²⁺ ions are ordered antiferromagnetically and that the exchange interactions involving the Ln³⁺ ions are relatively weak. The deviations from the Curie-Weiss law in Pr₂CuO₄ and Nd₂CuO₄ are in qualitative agreement with the predicted behavior for isolated Ln³⁺ ions under the influence of a crystal field. Hence these compounds provide interesting examples of planar Cu²⁺-ion antiferromagnets.