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Register a new userInvestigation into the Itinerant metamagnetism of Sr3Ru2O7 for the Field Parallel to the Ruthenium Oxygen Planes
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We report a detailed investigation into the metamagnetism of Sr3Ru2O7 at low temperatures for the magnetic field parallel to the ruthenium oxygen planes. The metamagnetism is studied as a function of temperature, magnetic field and sample quality using magnetisation, magnetotransport and specific heat as probes. From hysteretic behaviour in the magnetisation, we confirm earlier work and observe a finite temperature critical point at (5 T, >0.25 K). In our highest quality samples two-step metamagnetic transitions are additionally observed at 5.8 T and at 6.3 T, which coincide with a range of broad maximum in the magnetoresistance. At low temperatures, these two metamagnetic features each further split in two. Such behaviour of the multiple transitions are qualitatively different from the first order transition at 5.1 T.
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The magnetic and electronic properties of Eu2Ru2O7 are discussed in terms of the local ruthenium and europium coordinations, electronic band structure calculations and molecular orbital energy levels. A preliminary electronic structure was calculated within the LDA and LSDA+U approximations. The molecular orbital energy level diagrams have been used to interpret the Eu-Ru ligand spectrum and the ensuing magnetic properties. The orbital hybridizations and bonds are discussed.
We report the results of low temperature transport, specific heat and magnetisation measurements on high quality single crystals of the bilayer perovskite Sr3Ru2O7, which is a close relative of the unconventional superconductor Sr2RuO4. Metamagnetism is observed, and transport and thermodynamic evidence for associated critical fluctuations is presented. These relatively unusual fluctuations might be pictured as variations in the Fermi surface topography itself. No equivalent behaviour has been observed in the metallic state of Sr2RuO4.
The low-energy electronic structure of the itinerant metamagnet Sr3Ru2O7 is investigated by angle resolved photoemission and density functional calculations. We find well-defined quasiparticle bands with resolution limited line widths and Fermi velocities up to an order of magnitude lower than in single layer Sr2RuO4. The complete topography, the cyclotron masses and the orbital character of the Fermi surface are determined, in agreement with bulk sensitive de Haas - van Alphen measurements. An analysis of the dxy band dispersion reveals a complex density of states including van Hove singularities (vHs) near the Fermi level; a situation which is favorable for magnetic instabilities.
The strongly exchange enhanced Pauli paramagnet LaCo$_9$Si$_4$ is found to exhibit an itinerant metamagnetic phase transition with indications for metamagnetic quantum criticality. Our investigation comprises magnetic, specific heat, and NMR measurements as well as ab-initio electronic structure calculations. The critical field is about 3.5 T for $H||c$ and 6 T for $Hbot c$, which is the lowest value ever found for rare earth intermetallic compounds. In the ferromagnetic state there appears a moment of about 0.2 $mu_B$/Co at the $16k$ Co-sites, but sigificantly smaller moments at the 4d and $16l$ Co-sites.
Applying a magnetic field in the hexagonal plane of YMn$_6$Sn$_6$ leads to a complex magnetic phase diagram of commensurate and incommensurate phases, one of which coexists with the topological Hall effect (THE) generated by a unique fluctuation-driven mechanism. Using unpolarized neutron diffraction, we report on the solved magnetic structure for two previously identified, but unknown, commensurate phases. These include a low-temperature, high-field fan-like phase and a room-temperature, low-field canted antiferromagnetic phase. An intermediate incommensurate phase between the fan-like and forced ferromagnetic phases is also identified as the last known phase of the in-plane field-temperature diagram. Additional characterization using synchrotron powder diffraction reveals extremely high-quality, single-phase crystals, which suggests that the presence of two incommensurate magnetic structures throughout much of the phase diagram is an intrinsic property of the system. Interestingly, polarized neutron diffraction shows that the centrosymmetric system hosts preferential chirality in the zero-field double-flat-spiral phase, which, along with the THE, is a topologically non-trivial characteristic.
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