Crystal and magnetic structure ofCa3Ru2O7

Abstract

The crystal structure of the double-layered Ca 3 Ru 2 O 7 has been studied by convergent beam electron diffraction and powder neutron diffraction. The temperature dependence of the diffraction pattern reveals that all the lattice constants jump at the first-order metal-nonmetal transition at 48 K without a change of the space group symmetry of Bb2 1 m. In the neutron diffraction experiment, an additional magnetic reflection emerges below the Néel temperature, 56 K. A possible model for this antiferromagnetic ordering is proposed, in which model magnetic moments align ferromagnetically within the double layer and antiferromagnetically between the double layers. This model reasonably explains the characteristic field dependence of the magnetoresistance observed at around 6 T.

Magnetic phase transitions and bulk spin-valve effect tuned by in-plane field orientation in Ca3Ru2OFobes1, Jin2, Qu3 et al. 2011Phys. Rev. B10190View full textAdd to dashboardCite

“…24 Below the spin-flop transition field B c , the probed AFM structure is consistent with the model previously proposed for Ca 3 Ru 2 O 7 by DFT calculations 23 and powder neutron diffraction studies, 14 i.e. FM bilayers, with magnetic moments oriented along the b-axis, are stacked antiferromagnetically along the c-axis (This phase was labeled AFM-b in Ref.…”

“…Such a switch of magnetic easy-axis across the AFM-a/AFM-b phase boundary was initially identified in magnetization measurements by Cao et al, 12 and later confirmed by neutron scattering measurements. 14,24 Neutron scattering studies have also revealed that the giant/colossal magnetoresistance originates from the spin flop transition from the AFM-b to CAFM phase 24 . This indicates that interlayer spin scattering dominates electronic transport properties in Ca 3 Ru 2 O 7 .…”

“…It orders antiferromagnetically at T N = 56 K, 12,13 where moments are ferromagnetically ordered in the bilayers coupled antiferromagnetically along the c-axis. 14 The AFM phase transition is closely followed by a first order metal-insulator (MI) transition at T MIT = 48 K, 12,13 with a quasi-two-dimensional metallic state observed for T < 30 K. 15,16 Photoconductivity and Raman spectroscopy measurements revealed the MI transition to be associated with the opening of a charge gap 15,17 and suggested orbital ordering. [17][18][19] Resonant x-ray scattering studies suggest that while the orbital order parameter in Ca 3 Ru 2 O 7 is substantially weaker than in Ca 2 RuO 4 , weak orbital order combined with strong spinorbit coupling lead to the rich ground state properties of Ca 3 Ru 2 O 7 .…”

Carrier localization and electronic phase separation in a doped spin-orbit-driven Mott phase in Sr3(Ir1–xRux)2O7

“…A tilt already necessarily exists for the c axis-aligned moments in the canted AF phase, and the strong spin-lattice coupling in perovskite iridates 17 supports the notion of an accompanying structural tilt. Such a tilt likely renders Sr-327 isostructural to Ca 3 Ru 2 O 7 (space group: Bb2 1 m) 18 ; however, a full neutron data set and structural refinement have yet to be carried out.…”

CaCrO3: An Anomalous Antiferromagnetic Metallic Oxide

“…The rare observations of ferromagnetism in insulating transition-metal oxides most often are due to a particular type of orbital ordering [2]. The few examples of antiferromagnetic (AFM) metals, e.g., (La/Sr) 3 Mn 2 O 7 [3] or Ca 3 Ru 2 O 7 [4], are characterized by reduced electronic and structural dimensionality, and the antiferromagnetic order corresponds to a stacking of ferromagnetic (FM) layers. Here we report the discovery of a three-dimensional transition-metal oxide with metallic conductivity, antiferromagnetic exchange interactions, and C-type antiferromagnetic order: the perovskite CaCrO 3 .…”