过渡金属氧化物-刘俊明.ppt

LSSMS, PLD-Lab. PLD Lab, / LSSMS, PLD Lab. J. –M. Liu (刘俊明)Email: liujm@ Group page / 4d/5d oxides: T=Ru as an example from GC, MPLB (2008) Simplified phase diagram for (Ca,Sr)n+1RunO3n+1 Rich phases competing to each other, depending on n G. Cao et al. MPLB22, 19 (2008) 4d/5d oxides: T=Ru as an example Very different behaviors between Sr- Ca-based systems 4d/5d oxides: phenomena possible physics in n=2 Crystal fields Hund’s rule interactions p-d electron hybridization Electron-lattice coupling Spin-orbital coupling (~0.4 eV (5d), 0.1 eV (4d), 0.02 eV (3d)) A set of balances between different degrees of freedom A wide range of novel physical phenomena surprisingly in one material Highly anisotropic behaviors Mott-like transition Antiferromagnetic metallic state Metamagnetism Colossal magnetoresistance Bulk spin-valve effect Quantum oscillations H-oscillation Nonlinear conduction 4d/5d oxides: phenomena possible physics in n=2 b-axis is the easy axis For B//b, ?c drops at M-switching due to the spin-polarized transition. Then ?c increases due to the spin-orbit ordering For B//a, a rapid drop at B~15T For B//c, the Shubnikov-de Haas (SdH) oscillations The fully spin-polarized state may not be the most favored state for conduction. Ca3Ru2O7 4d/5d oxides: phenomena possible physics in n=2 Very soft orbital order (OO) and spin order (SO) Delicate inter-coupling between these orders allow very different ground states and transport behaviors Effect of orbital ordering here seems extremely remarkable 4d/5d oxides: phenomena possible physics in n=2 Cr-doping induces the extends the AFM-M state Cr-doping allows the spin cant at low B Bulk spin valve effect 4d/5d oxides: phenomena possible physics in n=2 Quantum oscillation (SdH effect) Fine Landau level in response to external magnetic field Multiferroic oxides Multiferroics: motivation Multiferroics: spin/polarization exclusion + - + Partially filled d shells break Time reversal symmetry N. A. Hill, Why are the