We report a comprehensive study of magnetic properties of Ni3TeO6. The system crystallizes in a noncentrosymmetric rhombohedral lattice, space group R3. There are three differently coordinated Ni atoms in the unit cell. Two of them form an almost planar honeycomb lattice, while the third one is placed between the layers. Magnetization and specific heat measurements revealed a single magnetic ordering at T-N = 52 K. Below TN the susceptibility with the magnetic field parallel to the c axis drops towards zero while the perpendicular susceptibility remains constant, a characteristic of antiferromagnetic materials. Neutron diffraction confirmed that the system is antiferromagnet below T-N with ferromagnetic ab planes stacked antiferromagnetically along the c axis. All Ni moments are in the S = 1 spin state and point along the c axis.

/pdf/ni3teo6-a-collinear-antiferromagnet-with-ferromagnetic-2s8ixbma6l.pdf

Ni3TeO6-a collinear antiferromagnet with ferromagnetic honeycomb planes

We have studied the far‐infrared spectra of 12 different gases trapped in the cages of β‐quinol clathrates. The data are most extensive for Ar, Kr, Xe, CO, N2, NO, and O2 in the frequency range from 15 to 85 cm−1. In these cases, monatomic and nonpolar diatomic gas molecules show a single absorption line, which we have assigned to translational motion of the molecule within its cage. Polar diatomic molecules show an additional line, which we have assigned to hindered rotation. These lines are an order of magnitude less intense than ordinary electric dipole transitions. The absorptions due to translational motion arise through dipole moments induced by interaction between the gas molecule and the clathrate cage. The frequencies and shapes of the infrared absorptions as a function of temperature from 1.2° to 170°K, as well as the frequencies of hindered rotation for N2 and O2 deduced from other experiments, were used to evaluate the parameters of potential‐well models for these seven gases. The specific hea...

Far‐Infrared Spectra of Gas Molecules Trapped in β‐Quinol Clathrates

We present an overview of recent results from nonresonant magnetic diffraction experiments on the antiferromagnetic compounds ${\mathrm{MnF}}_{2},$ ${\mathrm{FeF}}_{2},$ ${\mathrm{CoF}}_{2},$ and ${\mathrm{NiF}}_{2}$ using high-energy synchrotron radiation of photon energies above 100 keV. New results are presented on the determination of the spin and of the $L/S$ ratio for ${\mathrm{CoF}}_{2}$ and ${\mathrm{NiF}}_{2}.$ For ${\mathrm{CoF}}_{2},$ the saturation value of the long-range-ordered pure spin ${S}_{z}$ component ${S}_{z}=1.11(1)$ is considerably lower than the value ${S}_{z}=3/2$ for the free ${\mathrm{Co}}^{2+}$ ion. This is in contrast to our results for ${\mathrm{NiF}}_{2},$ where the full spin of the free transition-metal ion was found, ${S}_{z}=0.98(1).$ The temperature dependence of the magnetization in the critical region as well as in the low-temperature region is also presented. For all compounds, Ising behavior is found in the critical regime, whereas the crossover to the low-temperature spin-wave behavior varies. We attribute this to different anisotropies in this series of compounds.

/pdf/magnetic-properties-of-transition-metal-fluorides-mf2-m-mn-1wu07y0vry.pdf

Magnetic properties of transition metal fluorides MF2 (M = Mn, Fe, Co, Ni) via high-energy photon diffraction

Infrared reflection and transmission as a function of temperature have been measured on single crystals of Cu3Bi(SeO3)(2)O2Cl. The complex dielectric function and optical properties along all three principal axes of the orthorhombic cell were obtained via Kramers-Kronig analysis and by fits to a Drude-Lorentz model. Below 115 K, 16 additional modes [8(E parallel to(a) over cap)+ 6(E parallel to(b) over cap)+ 2(E parallel to(c) over cap)] appear in the phonon spectra; however, powder x-ray diffraction measurements do not detect a new structure at 85 K. Potential explanations for the new phonon modes are discussed. Transmission in the far infrared as a function of temperature has revealed magnetic excitations originating below the magnetic ordering temperature (T-c similar to 24 K). The origin of the excitations in the magnetically ordered state will be discussed in terms of their response to different polarizations of incident light, behavior in externally applied magnetic fields, and the anisotropic magnetic properties of Cu3Bi(SeO3)(2)O2Cl as determined by dc susceptibility measurements.

http://www.physics.ufl.edu/~tanner/PDFS/Miller12prb-CBSCO.pdf

P. L. Richards

Papers

Far-Infrared Magnetic Resonance in Ni F 2