Thermal and magnetic properties of Cu4O(SeO3)3 composed by ferrimagnetic O2Cu6 units of edge-sharing OCu4 tetrahedra.

Monoclinic Cu 4 O(SeO3) 3 has been prepared hydrothermally with subsequent heating in evacuated silica tubes. It has been characterized in measurements of dc and ac magnetic susceptibility χ and specific heat C p. The title compound orders magnetically at T 1 = 13.2 K and evidences a pre-transitional anomaly at T 2 = 17.2 K. In the range T 1 < T < T 2 , the application of external magnetic field rapidly suppresses excessive magnetization of this intermediate phase, but the hump in specific heat appears. The magnetic system of the title compound is constituted by the layered network of isolated Cu atoms and O 2 Cu 6 units composed by edge-sharing anion-centered OCu 4 tetrahedra. First principles calculations provided values of both ferromagnetic and antiferromagnetic exchange interactions within O 2 Cu 6 units J 1 – J 11 and J 12 – J 22 , and antiferromagnetic intralayer J 23 – J 30 and interlayer J 31 – J 32 exchange interactions. Basing on signs and values of these interactions a magnetic model of monoclinic Cu 4 O(SeO3) 3 is suggested. • O 2 Cu 6 units of edge-sharing OCu 4 tetrahedra are the building blocks of Cu 4 O(SeO3) 3. • It orders magnetically at T 1 = 13.2 K and shows a pre-transitional anomaly at T 2 = 16.5 K. • Basing on signs and values of exchange interactions a magnetic model is suggested. [ABSTRACT FROM AUTHOR]