Atomic-Scale Fingerprint of Mn Dopant at the Surface of Sr3(Ru1−xMnx)2O7

Abstract

Chemical doping in materials is known to give rise to emergent phenomena. These phenomena are extremely difficult to predict a priori, because electron-electron interactions are entangled with local environment of assembled atoms. Scanning tunneling microscopy and low energy electron diffraction are combined to investigate how the local electronic structure is correlated with lattice distortion on the surface of Sr3(Ru1−xMnx)2O7, which has double-layer building blocks formed by (Ru/Mn)O6 octahedra with rotational distortion. The presence of doping-dependent tilt distortion of (Ru/Mn)O6 octahedra at the surface results in a C2v broken symmetry in contrast with the bulk C4v counterpart. It also enables us to observe two Mn sites associated with the octahedral rotation in the bulk through the “chirality” of local electronic density of states surrounding Mn, which is randomly distributed. These results serve as fingerprint of chemical doping on the atomic scale.

Emergent charge order near the doping-induced Mott-insulating quantum phase transition in Sr3Ru2O7

“…Conductance maps g(r, V) reveal a bi-directional long-range checkerboard charge modulations ( Fig.2(e)); particularly V=-40meV and V=-100meV maps) embedded within the long-wavelength inhomogeneity. The absence of this charge ordering in the real space images of the x=1% sample ( Fig.2(b)), as well as in earlier STM experiments on the undoped [11,24] and Mndoped compound at 100 K [20], indicate its origin not to be related to any surface reconstruction, rather to an electronic instability induced by Mn-doping at low temperatures. Further indication of the electronic nature of the ordering phenomenon can be concluded by the absence of any structural peaks, corresponding to the observed modulations, in neutron scattering [14], in recent low energy electron diffraction (LEED) [20], and in non-resonant hard x-ray scattering [18].…”

Half-metallic ferromagnetism in Sr3Ru2O7

“…For instance, the bilayer member Sr 3 Ru 2 O 7 (n=2) shows metamagnetic transitions, 2 quantum critical phenomena, 3 and electronic nematic phases. 4 In addition, the physical properties of the system can be manipulated via external parameters (temperature, pressure, magnetic field, ...) [5][6][7] or by defects and alloying [8][9][10][11][12][13] to produce metal-to-insulator or magnetic phase transitions. To determine and control these properties requires an understanding of the ground-state structure and the role of RuO 6 octahedra rotations in the system.…”

Zigzag and Checkerboard Magnetic Patterns in Orbitally Directional Double-Exchange Systems

“…In this context, new phenomena have recently been observed and investigated in hybrid oxides with partial substitution of inequivalent TM ions [14][15][16][17][18]. Particularly fascinating are the Mndoped layered Sr ruthenates that represent a paradigmatic example of nontrivial coupling between itinerant ferromagnetic (FM) and localized antiferromagnetic (AF) degrees of freedom [19,20] in the doped t 2g sector with a resulting metal-insulator transition (MIT) [20-23] and magnetic order [19,20,22,[24][25][26] that are decoupled and robust over a large range of doping [21,22,25].In this Letter, we show general features of orbitally directional double-exchange (DE) layered systems as a novel metal-to-insulator transition and two predominant types of orderings within the phase diagram. The DE mechanism is known to be at the origin of itinerant ferromagnetism in e g systems and, when the superexchange between localized spins is considered, to yield exotic magnetic structures [9,[27][28][29][30][31][32][33][34] and other states based on electronic self-organization [11,35], whose stability often relies on additional microscopic couplings, and is confined to specific electron densities.…”

“…In this context, new phenomena have recently been observed and investigated in hybrid oxides with partial substitution of inequivalent TM ions [14][15][16][17][18]. Particularly fascinating are the Mndoped layered Sr ruthenates that represent a paradigmatic example of nontrivial coupling between itinerant ferromagnetic (FM) and localized antiferromagnetic (AF) degrees of freedom [19,20] in the doped t 2g sector with a resulting metal-insulator transition (MIT) [20-23] and magnetic order [19,20,22,[24][25][26] that are decoupled and robust over a large range of doping [21,22,25].…”