Showing papers by "Joshua E. Goldberger published in 2008"
TL;DR: In this article, the perovskites Sr2MnRuO6 (Sr, La; M=Cr, Mn, Fe, Co, Ni) and LaSrMnRO6 have been investigated and their properties compared with those of the broader family of A2MRuO6 double perovsites.
Abstract: The perovskites Sr2MnRuO6 and LaSrMnRuO6 have been investigated and their properties compared with those of the broader family of A2MRuO6 double perovskites (A=Sr, La; M=Cr, Mn, Fe, Co, Ni). Neutron powder diffraction shows that both phases lack long-range Mn/Ru order. Sr2MnRuO6 exhibits a cooperative Jahn–Teller distortion, conductivity that proceeds via variable-range hopping, and antiferromagnetic (AFM) order (C-type structure, TN≅200K, 2.05(1) μB per transition metal). LaSrMnRuO6 exhibits nearly undistorted octahedra, conductivity that proceeds via diffusion-assisted small-polaron hopping, and ferromagnetic (FM) order (TC≅220K, 1.60(4) μB transition metal). Band structure calculations show that AFM Mn–O–Ru coupling optimizes polarization of the Ru t2g orbitals, while FM coupling favors delocalization of the Ru t2g electrons. The transition from antiferromagnetism to ferromagnetism is linked to a loss of orbital order and stabilized over competing glassy states by delocalization of Ru t2g electrons.
28 citations