相关论文: Lattice instabilities in cubic pyrochlore Bi$_2$Ti…

Pyrochlore dielectric materials such as (Bi$_{1.5}$Zn$_{0.5}$)(Nb$_{1.5}$Zn$_{0.5}$)O$_7$ (BZN) have generated interest because they combine high dielectric constants with small dielectric loss tangents and yet are cubic at all…

We investigated the possibility of temperature dependent lattice distortions in the pyrochlore compound Tb$_{2}$Ti$_{2}$O$_{7}$ by measuring the internal magnetic field distribution, using muon spin resonance, and comparing it to the…

We report the X-ray study for the pyrochlore oxide Cd2Re2O7. Two symmetry-lowering structural transitions were observed at Ts1=200K and Ts2=120K. The former is of the second order from the ideal cubic pyrochlore structure with space group…

The cubic, stoichiometric oxide compounds Bi2Ti2O6O' (also written Bi2Ti2O7) and Bi2Ru2O6O' (also written Bi2Ru2O7) have in common lone-pair active Bi3+ cations on the pyrochlore A-site with a propensity to off-center. Unlike Bi2Ti2O6O',…

The phonon dispersion relation of NiTi in the simple cubic B2 structure is computed using first-principles density-functional perturbation theory with pseudopotentials and a plane-wave basis set. Lattice instabilities are observed to occur…

Ab initio phonon calculations for the nonpolar reference structures of the (001), (110), and (111) PbZrO_3/PbTiO_3 [1:1] superlattices are presented. The unstable polar modes in the tetragonal (001) and (110) structures are confined in…

We study the pyrochlore series (Eu$_{1-x}$Bi$_x$)$_2$Ir$_2$O$_7$ for $ 0 \leq x \leq 1$. We show that for small $x$, the lattice undergoes an anomalous contraction but the all-in/all-out and metal-to-insulator transitions remain robust, and…

In this article we report the structural stability of Er$_2$Ti$_2$O$_7$ cubic pyrochlore with pressure using x-ray diffraction, Raman spectroscopy, photoluminescence, x-ray absorption and ab-initio calculations. Our studies establish a…

Although materials that exhibit nearest-neighbor-only antiferromagnetic interactions and geometrical frustration theoretically should not magnetically order in the absence of disorder, few such systems have been observed experimentally. One…

We have performed detailed first-principles calculations to determine the eigenvectors of the zone-center modes of hexagonal BaTiO3 and shown that the experimentally relevant low-energy modes (including the non-polar instability) can be…

The pyrochlore compound \tbti\ is known to remain in a spin-liquid state down to the lowest attainable temperature (0.05\,K), whereas current theories predict it should order into an antiferromagnetic structure. A number of models have been…

In the pyrochlore compounds, Tb$_2$Ti$_2$O$_7$ and Tb$_2$Sn$_2$O$_7$, only the Tb$^{3+}$ ions are magnetic. They exhibit quite abnormal -- and, in view of their chemical similarity, strikingly different -- magnetic behaviour, as probed by…

The ordered hexagonal perovskite Ba2CuTeO6 hosts weakly coupled S=1/2 spin ladders produced by an orbital ordering of Cu2+. The magnetic susceptibility chi(T) of Ba2CuTeO6 is well described by that expected for isolated spin ladders with…

We report on the epitaxial growth, structural and electrical properties of metallic pyrochlore bismuth ruthenate heterostructures grown along both the [001] and [111] directions. Ordered pyrochlore thin films were obtained with highly…

We present a first-principles investigation of ferroelectricity in layered perovskite oxide La2Ti2O7 (LTO), one of the compounds with highest Curie temperature known (1770 K). Our calculations reveal that LTO's ferroelectric transition…

Both amorphous and crystalline materials frequently exhibit low temperature specific heats in excess of what is predicted using the Debye model. The signature of this excess specific heat is a peak observed in $C/T^3$ \textit{versus} $T$.…

A hidden order that emerges in the frustrated pyrochlore Tb$_{2+x}$Ti$_{2-x}$O$_{7+y}$ with $T_{\text{c}}=0.53$ K is studied using specific heat, magnetization, and neutron scattering experiments on a high-quality single crystal.…

A new series of cubic double perovskites Ba$_2R_{2/3}$TeO$_6$ ($R$ = Y, La, Pr, Nd, Sm-Lu) was synthesized via solid state reaction. The $R^{3+}$ and Te$^{6+}$ ions are ordered on alternating octahedral sites, with the rare earth sites 2/3…

We report physical property characterization of Bi2-xMxRu2O7 pyrochlores, including magnetic suseptibility, resistivity, and Seebeck coefficients. The solid solution exists up to x=0.5 for (M=Cu,Ni,Co) and up to x=0.1 for (M=Fe,Mn). None of…

The pyrochlore antiferromagnet Tb2Ti2O7 has proven to be an enigma to experimentalists and theorists working on frustrated magnetic systems. The experimentally determined energy level structure suggests a local <111> Ising antiferromagnet…