Magnetic properties of Sr2LnRuO6 (Ln=Tb, Ho)

Magnetic properties of ordered perovskite-type compounds Sr2LnRuO6 (Ln=Tb, Ho) have been investigated. The magnetization and specific heat measurements show the existence of magnetic transitions at 41 K for Sr2TbRuO6 and at 36 K for Sr2HoRuO6. Powder neutron diffraction measurements were performed for Sr2TbRuO6 at 10 K and room temperature, and for Sr2HoRuO6 at 10 K, 25 K and room temperature. The crystal structure at room temperature is monoclinic with space group P21/n, and the Ru5+ and Ln3+ ions are structurally ordered at the B sites of the ABO3 perovskite-type structure. Data collected at low temperatures show that these compounds have a long range antiferromagnetic ordering involving both Ru5+ and Ln3+. Each magnetic moment of these ions orders in a Type I arrangement and they are antiparallel with each other in the ab-plane. The direction of the magnetic moments for Sr2HoRuO6 is along the c axis, while that for Sr2TbRuO6 is canted from the c axis by about 20deg. The ordered magnetic moments at 10 K for Sr2TbRuO6 are 3.0(1) μB (Ru5+) and 5.0(1) μB (Tb3+), and those at 10 K for Sr2HoRuO6 are 2.74(9) μB (Ru5+) and 6.66(8) μB (Ho3+). (author)