[en] Dimethylammonium copper (II) chloride (also known as DMACuCl₃ or MCCL) is a low dimensional S=12 quantum spin system proposed to be an alternating ferro-antiferromagnetic chain with similar magnitude ferromagnetic (FM) and antiferromagnetic (AFM) exchange interactions. Subsequently, it was shown that the existing bulk measurements could be adequately modeled by considering DMACuCl₃ as independent AFM and FM dimer spin pairs. We present here new inelastic neutron scattering measurements of the spin excitations in single crystals of DMACuCl₃. These results show significant quasi-one-dimensional coupling, however the magnetic excitations do not propagate along the expected direction. We observe a band of excitations with a gap of Δ=0.95 MeV and a bandwidth of 0.82 MeV

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[en] Zero field (ZF) and transverse field (TF) muon spin relaxtion and rotation (μSR) experiments have been carried out in the Cd-doped heavy fermion super conductor CeCoIn₅ to investigate its superconducting state.

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[en] High field magnetizations up to 100 T, lattice constants and electronic specific heat coefficients have been measured for the Laves phase Lu(Co_1-xM_x)₂ (M=Ga, Sn and Si) compounds which exhibit itinerant electron metamagnetism for small x. The lattice constant increases with increasing x for M=Ga or Sn, while it decreases linearly in the case of M=Si. The metamagnetic characteristics strongly depend on the substitutional element M. The critical field for the metamagnetic transition decreases with increasing x for M=Ga and Si, whereas it remains constant around 40 T above x=0.06 for M=Sn. The magnetization jump due to the transition increases for M=Sn and rapidly decreases for M=Si. The different characteristics may result from the difference in the shape of the density of states modified by the substitutional element. ((orig.))

[en] Optical absorption spectra of yellow series excitons in cuprous oxide were measured with right and left circularly polarized light in magnetic fields up to 4.5 T generated by a superconducting magnet. Magneto-oscillatory spectra were observed in the high magnetic field and short wavelength region above the hydrogenic series. The Zeeman splittings of the hydrogenic series are equal to those of the magneto-oscillatory spectra. Energies of the diamagnetic term of the hydrogenic series are also equal to the cyclotron energy of the magneto-oscillatory spectra. It is concluded from these facts that the two absorption spectra are due to transitions to the same excitonic states. ((orig.))

[en] Far- and mid-infrared properties of antiferromagnetic Y_1-xRE_xBa₂Cu_3-yZn_yO₆ (RE=Pr, Gd, x=0 and 0.8; y=0 and ∼0.15) were investigated by infrared reflection and transmission measurements (k parallel c-axis). All six phonon modes of E_u symmetry and several multi-phonon bands were observed. Zn substitution causes phononside bands and a surprising temperature dependence of multi-phonon bands, possibly due to spin-lattice interactions. All compounds show several features in the mid-infrared range that might be related to bimagnon-plus-phonon absorption. (orig.)

[en] The electronic properties of the cuprate superconductors have been studied by measuring the reflectance over the frequency range from the far-infrared to the near-ultraviolet (roughly, 10 meV-5 eV). There is an interesting behavior in both the normal state and the superconducting state. In the normal state, there is the well-known non-Drude distribution of the doping-induced spectral weight. In the superconducting state, the spectral weight of the superconducting condensate correlates with T_c in a variety of materials. Remarkably, in optimally doped superconductors, only about 20% of the doping-induced carriers joins the superfluid; the rest of the spectral weight remains at finite frequencies. (orig.)

[en] We have performed elastic neutron scattering studies of the quantum critical antiferromagnet Cr0.963V0.037. We have found that unlike pure Cr, which orders at two incommensurate wave vectors, Cr0.963V0.037 orders at four incommensurate and one commensurate wave vectors. We have found strong temperature dependent scattering at the commensurate and incommensurate wave vectors below 250 K. Results indicate that the primary effect of V doping on Cr is the modification of the nesting conditions of the Fermi surface and not the decreasing of the Neel temperature

[en] Ferrite powder samples of Cr_xFe_3−xO₄ (0.0≤x≤1.0) were prepared by chemical co-precipitation, and calcined in a tube furnace with argon-flow at 1723 K for 2 h. X-ray diffraction patterns indicated that all the samples had an (A)[B]₂O₄ single phase cubic spinel structure with a Fd3^¯m space group. Magnetic measurements indicated that the magnetization of the samples decreased with the Cr doping level. A new model for the magnetic ordering in these samples was employed to explain the dependence of the magnetization and cation distribution on the Cr doping level; namely, taking into consideration constraints arising from Hund's rules and from the spin direction of the itinerant 3d electrons, the directions of the Cr²⁺ and Cr³⁺ cation magnetic moments were taken to lie antiparallel to the moments of the Fe cations within the same sub-lattice (A or B sub-lattice).