A single crystal of Sr5Ru5-xO15 (x = 0.90(2)) with mixed valence of Ru(IV) and Ru(V) was synthesized under a high pressure of 4 GPa with an oxidizer. Sr5Ru5-xO15 crystallizes in a hexagonal perovskite-type structure with a space group P63/mmc (No.194), a = 5.5600(11) Å, and c = 22.830(5) Å. An alternative stacking of four corner-sharing (c) SrO3 layers and one face-sharing (h) SrO3 layer linking RuO6 octahedra and its doubling along c-axis gives a 10 layer period hexagonal cell (10H) which is denoted by (cccch)2. The partial deficiency of Ru found in face-sharing octahedra, as reported for 8H-Sr4Ru4-xO 12 (x = 0.95) with (ccch)2 stacking, yields an average Ru valence estimate of 4.87. The bond valence analysis indicates that the valence of Ru in fully corner-sharing octahedra is nearly 5, while that of Ru in face-sharing octahedra is considerably lower than 5. This compound is a weakly ferromagnetic metal with Curie temperature Tc = 160 K and a saturated moment of 0.07 and 0.05 μB/Ru in H ⊥ c and H // c, respectively. In the ferromagnetic state, we found remarkable enhancement of the coercivity below 50 K. At 1.7 K, a giant coercive field of ∼12 T was observed. We argue that Ru(IV,V) in face-sharing layers are responsible for the ferromagnetism and that possible glassy character due to frustration and disorder may at least in part contribute to the giant coercivity.
ASJC Scopus subject areas
- 化学 (全般)