Magnetic and neutron diffraction study on ordered perovskites Sr(2)LnRuO(6) (Ln=Tb, Ho)

Magnetic properties of ordered perovskite-type compounds Sr(2)LnRuO(6) (Ln= Tb, Ho) are reported. Powder neutron diffraction measurements at 10 K, 25 K and room temperature were performed to investigate their crystal and magne tic structures. Both of these compounds are distorted perovskites with spac e group P2(t)/n and a 1:1 ordered arrangement of Ln(3+) and Ru5+ over the s ix-coordinate sites. Data collected at 10 K and 25 K show that they have a long range antiferromagnetic ordering involving both Ln(3+) and Ru5+. Each of these ions orders in a Type I arrangement. The direction of the magnetic moments is along the c-axis for Sr2HoRuO6, while it is canted by ca. 20 de grees from the c-axis for Sr2TbRuO6. The magnetic susceptibility and specif ic heat measurements show the existence of magnetic transitions at 41 K for Sr2TbRuO6 and at 36 K for Sr2HoRuO6. The held-dependence of the magnetizat ion was measured and a small hysteresis loop was found below magnetic trans ition temperatures, indicating the existence of a weak ferromagnetic moment associated with the antiferromagnetism. (C) 2001 Elsevier Science B.V. All rights reserved.