Surface and bulk structural properties of single-crystallineSr3Ru2O7

Abstract

We report temperature and thermal-cycling dependence of surface and bulk structures of double-layered perovskite Sr 3 Ru 2 O 7 single crystals. The surface and bulk structures were investigated using low-energy electron diffraction (LEED) and single-crystal X-ray diffraction (XRD) techniques, respectively. Single-crystal XRD data is in good agreement with previous reports for the bulk structure with RuO 6 octahedral rotation, which increases with decreasing temperature (~ 6.7(6) at 300 K and ~ 8.1(2) at 90 K). LEED results reveal that the octahedra at the surface are much more distorted with a higher rotation angle (~ 12 between 300 and 80 K) and a slight tilt ((4.5±2.5) at 300 K and (2.5±1.7) at 80 K). While XRD data confirms temperature dependence of the unit cell height/width ratio (i.e. lattice parameter c divided by the average of parameters a and b) found in a prior neutron powder diffraction investigation, both bulk and surface structures display little change with thermal cycles between 300 and 80 K. PACS number(s): 61.05.cp, 61.05.jh, 68.47.Gh Page 2 of 25The ruthenate Ruddlesden-Popper (RP) series Sr n+1 Ru n O 3n+1 (n = 1, 2, 3, …) exhibit rich electronic and magnetic properties covering a range from diamagnetic superconductor 1 (n = 1) to paramagnetic conductor with antiferromagnetic (AFM) correlation 2 (n = 2) to ferromagnetic (FM) metal 3,4 (n = 3, ∞). Extensive studies on the single-layered (n = 1) Sr 2 RuO 4 and the isovalently doped (Sr,Ca) 2 RuO 4 system reveal that the lattice degree of freedom plays a critical role in their physical properties, both in bulk 5,6 and on the surface 7,8,9 . Theoretical calculations 10 also indicate that the rotation and tilt of RuO 6 octahedra in (Sr,Ca) 2 RuO 4 are closely coupled to the ferromagnetism and antiferromagnetism, respectively. Therefore, precise determination of the structural properties of the RP series is the key towards understanding of their exotic physical properties.The motivation for investigating the structural properties of double-layered (n = 2) Sr 3 Ru 2 O 7 is multifold. First of all, it displays unique physical properties, different from the rest of the RP series. Although there is no long-range magnetic ordering under ambient pressure, a short-range AFM-type correlation develops below ~ 20 K, as probed by magnetic susceptibility 2,11 and neutron scattering measurements 12 . Application of hydrostatic and uni-axial pressure can drive the system into a ferromagnetically ordered state 11,13 . The application of magnetic field leads to similar result -the system undergoes a metamagnetic transition 14 . These clearly indicate that the system has two competing magnetic interactions (AFM versus FM), which are coupled with the structural properties. Second, the bulk crystal structure of Sr 3 Ru 2 O 7 has been modeled after data collection with various diffraction techniques into three different space groups since the first report in 1990 15 . The space groups reported include I4/mmm (tetragonal, No. 139) [15][16][17] Pban (...

Structure-property coupling in Sr3(Ru1−xMnx)Hu1, McCandless2, Garlea3 et al. 2011Phys. Rev. BSelf Cite321420View full textAdd to dashboardCite

“…For all Sr 3 (Ru 1−x Mn x ) 2 O 7 samples, single crystal XRD data show that their structure can be described by the space group I 4/mmm with the details described previously [15]. Fig.…”

Hidden phases revealed at the surface of double-layeredSr3(Ru1−xMChen1, Kim2, Nascimento3 et al. 2016Phys. Rev. BSelf Cite91110View full textAdd to dashboardCite

“…The ability to see the subsurface Mn atoms is a consequence of the tilt distortion of (Ru/Mn)O 6 octahedra at the surface [33], which reduces the symmetry from C 4v to C 2v , changing the electronic properties of the surface with respect to the bulk [34]. Fig.…”

“…1(a)), the ( ) LEED I-V structural analysis was performed using only the fractional order spots exploiting a procedure used previously [33]. Fractional ordered spots are more sensitive to rotation and tilt than the integer spots.…”

“…For instance, the previous studies of Ca 2-x Sr x RuO 4 showed that cleaving this material enhances RuO 6 rotational distortion and induces a buckling of the Ca/Sr-O surface plane, which suppresses electronic phase transition temperatures but avoid simultaneous lattice distortion, thus producing a purely electronic Mott transition for x=0.1 [31], as well as a much different phase diagram than the bulk [32]. It is understood from the previous work that RuO 6 rotation is enhanced and tilt is induced at the surface of Sr 3 (Ru 1-x Mn x ) 2 O 7 [33], which leads to a different electronic behavior [34]. Here we establish the surface structureproperty relationship.…”

Predicting hidden bulk phases from surface phases in bilayered Sr3Ru2O7

“…Using a combination of low-energy electron diffraction (LEED) and high-resolution electron energy loss spectroscopy (HREELS) analysis, we observed more distorted RuO 6 octahedra at the surface than in the bulk 18, 19 . These distortions are characterized by a higher rotation angle of 10.5° ± 3° and a tilt angle of 2.6° ± 0.8° producing a surface symmetry-breaking that leads to a reduced conducting state relative to the bulk.…”