Physics of Transition Metal Oxides

Fingerprints of spin-orbital physics in cubic Mott insulators: Magnetic exchange interactions and optical spectral weights

“…Quite generally, the Coulomb interactions lead then to strong electron correlations which frequently involve orbitally degenerate states, such as 3d ͑or 4d͒ states in transition metal compounds, and are responsible for quite complex behavior with often puzzling transport and magnetic properties. 1 The theoretical understanding of this class of compounds, with the colossal magnetoresistance ͑CMR͒ manganites as a prominent example, 2,3 has substantially advanced over the last decade, 4 after it became clear that orbital degrees of freedom play a crucial role in these materials and have to be treated on equal footing with the electron spins, which has led to a rapidly developing field, orbital physics. 5 Due to the strong onsite Coulomb repulsion, charge fluctuations in the undoped parent compounds are almost entirely suppressed, and an adequate description of these strongly correlated insulators appears possible in terms of superexchange.…”

“…When the low-energy excitations are of CT type, two holes could also be created within a 2p orbital on a ligand ͑oxygen or fluorine͒ ion in between two transition metal ions, described by d i m p 6 7 and this has become a textbook example of spinorbital physics by now. 4,19 Orbital order occurs in KCuF 3 below the structural transition at T s ϳ 800 K. At T Ͻ T s the structure is tetragonal, with longer Cu-Cu distances within the ab planes ͑d ab = 8.28 Å͒ than along the c axis ͑d c = 7.85 Å͒, 49 which favors strong AF interactions along the c axis. Below the magnetic transition at T N Ӎ 38 K, long-range magnetic order of A type sets in, 50,51 and the ordered moment is 0 = 0.48 B .…”

“…Using the spin algebra ͑Clebsch-Gordon coefficients͒, and making a rotation of the terms derived for a bond ͗ij͘ ʈ c to the other two cubic axes a and b, one finds five contributions to H U ͑d 4 …”

Electronic states ofRFe2O4(R=Lu,Yb,TmLafuerza1, García2, Subı́as3 et al. 2014Phys. Rev. B10241View full textAdd to dashboardCite

“…Mixed-valence transition-metal oxides exhibit remarkable properties such as high temperature superconductivity, colossal magnetoresistance, and multiferroicity, which may give rise to important technological applications [1]. Their interesting features are the result of the complex coupling between spin, charge, lattice, and orbital degrees of freedom.…”

Possible high-pressure orbital quantum criticality and an emergent resistive phase in PbRuO3

“…3) and URhGe. 4 Transition metal oxides show many exotic conducting states and phase transitions 5 so a variety of quantum critical phenomena may be expected. QCPs in conducting oxides have been accessed by suppressing magnetic transitions, and are implicated in the emergence of superconductivity in doped antiferromagnetic cuprates, but the best established example is in the bilayer ruthenate Sr 3 Ru 2 O 7 .…”