Two new lanthanide members of francisite family Cu3Ln(SeO3)2O2Cl (Ln = Eu, Lu)

• Two francisites are synthesized: Cu3Ln(SeO3)2O2Cl, Ln = Eu and Lu.
• The arrangement of copper ions corresponds to buckled kagomé type lattice.
• New francisites reach antiferromagnetic order at low temperatures.

Two new lanthanide compounds, Cu3Ln(SeO3)2O2Cl, Ln = Eu and Lu, with mineral francisite structure were synthesized under vacuum in sealed quartz tubes. The Rietveld refinement of the structure results in orthorhombic unit cell, space group Pmmn. The arrangement of magnetically active Cu2+ ions in francisite structure corresponds to buckled kagomé type lattice. Both compounds were characterized in measurements of ac-magnetic susceptibility, dc-magnetization, X-band electron spin resonance and specific heat in the range 2–320 K under magnetic field up to 9 T. The ferromagnetic interactions dominate in both compounds at elevated temperatures. The Eu (Lu) francisite manifests antiferromagnetic order at TN = 36 (38) K and undergoes the field-induced metamagnetic transition into canted ferrimagnetic state at BC = 2.6 (3.0) T. The magnetization loops of both compounds evidence hysteretic behavior above BC.