Hexagonal R -type ferrites (Ba,Sr) M2±x T 4∓x O11 (M=Fe,Co; T=Ru,Ti) were studied via neutron and x-ray diffraction, magnetization, and electrical transport measurements. Magnetization data for single-crystal BaFe3.26 Ti2.74 O11 reveal two magnetic transitions at T1=250 K and T 2 =84 K, which indicates complex magnetic order driven by competing interactions on a frustrated lattice with a noncentrosymmetric structure. Magnetization data for single-crystal BaCo1.85 Ru4.15 O11 reveal soft ferromagnetic order at TC =105 K with an easy direction perpendicular to the c axis. Neutron diffraction data for polycrystalline BaCo1.68 Ru4.32 O11 indicate a nearly compensated arrangement of spins lying within the a-b plane with a possible canting out of the plane that yields nonzero scalar spin chirality. The transverse magnetoresistivity ρxy of single-crystal BaCo 1.85 Ru4.15 O11 for current J||H⊥c axis is typical of an anomalous Hall effect observed in ferromagnets, whereas for J||H⊥c axis, ρxy is a nonmonotonic function of the magnetic field, consistent with a topological Hall effect that depends upon scalar spin chirality. Neutron diffraction reveals transitions to ferrimagnetic order at TC =262 (1) K for single-crystal SrFe2.6 Ru3.4 O11, and at TC =403 K for polycrystalline SrFe 2.96 Ru3.04 O11 (refined as a collinear structure at T=5 K).
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|State||Published - May 17 2010|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics