Spin gap in Tl2Ru2O7 and the possible formation of Haldane chains in three-dimensional crystals

Abstract

Dimensionality is one of the most important parameters of physical phenomena. Only two things determine the universality class of a phase transition: the dimensionality of a given system and the symmetry of the order parameter. In most cases, the dimensionality of a substance is predetermined by its crystal structure. Examples in which the effective dimensionality is reduced are quite rare. Here we show that the three-dimensional cubic system of Tl(2)Ru(2)O(7) most probably evolves into a one-dimensional spin-one Haldane system with a spin gap below 120 K, accompanied by anomalies in the structure, resistivity and susceptibility. We argue that these anomalies are due to an orbital ordering of Ru 4d electrons, with a strong coupling among three degrees of freedom: orbital, spin and lattice. Our work provides a unique example of the spontaneous formation of Haldane system with an insight into the intriguing interplay of different degrees of freedom.

Magnetic moment suppression in Ba3CoRu2O9: Hybridization effect

“…14 The on-site Coulomb repulsion parameter U and the intra-atomic Hund's rule exchange J H were chosen as follows: U (Co) = 6 eV, J H (Co) = 1 eV, 15 U (Ru) = 3 eV, J H (Ru) = 0.7 eV. 10 In order to check the stability of the results these parameters were varied, as will be discussed. We used the mesh of the 144 k points in the full Brillouin zone in the course of the calculations.…”

Doping-Induced Ferromagnetism and Possible Triplet Pairing ind4Mott Insulators

“…Model.-There are a number of d 4 compounds, magnetic as well nonmagnetic, with various lattice structures [10][11][12][13][14][15][16][17]. To be specific, we consider a square lattice d 4 insulator lightly doped by electrons.…”

High-resolution structure studies and magnetoelectric coupling of relaxor multiferroicPb(Fe0.5Nb0.5)Sim1, Peets2, Lee3 et al. 2014Phys. Rev. BSelf Cite15060View full textAdd to dashboardCite

“…Fitting (shown by a solid line) results in a Debye temperature Θ D of only 150 K, whereas b = 1.5, V 0 = 64.582Å 3 , and Q = 3.87(6) × 10 −17 J are similar to parameters used for other materials [24][25][26]. We note that the resulting Debye temperature is abnormally small, leading to a bulk modulus around 600 GPa for a typical Grüneisen parameter of order one, which is high for an oxide: For example, we earlier found bulk moduli of 120 GPa for YMnO 3 [27] while 250 GPa has been reported for MgSiO 3 [28].…”