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Register a new userMagnetic properties of single-crystalline CeCuGa3
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The magnetic behavior of single-crystalline CeCuGa3 has been investigated. The compound forms in a tetragonal BaAl4-type structure consisting of rare-earth planes separated by Cu-Ga layers. If the Cu-Ga site disorder is reduced, CeCuGa3 adopts the related, likewise tetragonal BaNiSn3-type structure, in which the Ce ion are surrounded by different Cu and Ga layers and the inversion symmetry is lost. In the literature conflicting reports about the magnetic order of CeCuGa3 have been published. Single crystals with the centrosymmetric structure variant exhibit ferromagnetic order below approx. 4 K with a strong planar anisotropy. The magnetic behavior above the transition temperature can be well understood by the crystal-field splitting of the 4f Hunds rule ground-state multiplet of the Ce ions.
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Single crystal of CeMg$_{12}$ is obtained by Bridgman method. CeMg$_{12}$ crystallizes in the tetragonal structure with space group $I4/mmm$ (#139). The Laue pattern confirms the tetragonal crystal structure of CeMg$_{12}$. We have studied the magnetic properties by measuring magnetic susceptibility, magnetization, heat capacity and electrical transport. Specific heat measurement shows that the compound orders at 1.2 K. We have measured the magnetic susceptibility in the temperature range 1.8 to 300 K, and the susceptibility data show that [100] crystallographic direction is the easy axis of magnetization. At high temperature inverse susceptibility varies linearly with temperature, and follows the Curie-Weiss behaviour. The effective moment is close to the free ion value thus indicating Ce is in trivalent state in this compound.
We studied the properties of the antiferromagnetic (AFM) UNi0.5Sb2 (TN approx 161 K) compound in Sb-flux grown single crystals by means of measurements of neutron diffraction, magnetic susceptibility ({chi}), specific heat (Cp), thermopower (S), thermal conductivity ({kappa}), linear thermal expansion ({Delta}L/L), and electrical resistivity ({rho}) under hydrostatic pressures (P) up to 22 kbar. The neutron diffraction measurements revealed that the compound crystallizes in the tetragonal P42/nmc structure, and the value of the U-moments yielded by the histograms at 25 K is approx 1.85 pm 0.12 {mu}B/U-ion. In addition to the features in the bulk properties observed at TN, two other hysteretic features centered near 40 and 85 K were observed in the measurements of {chi}, S, {rho}, and {Delta}L/L. Hydrostatic pressure was found to raise TN at the rate of approx 0.76 K/kbar, while suppressing the two low temperature features. These features are discussed in the context of Fermi surface and hybridization effects.
The magnetic properties of perovskite CaVO3 single crystals have been studied by means of magnetoresistance r(T, H) and magnetization M(H) measurements in fields to 18T. At 2 K, the magnetoresistance is positive and a maximum value of Dr(18T)/r(0) = 16.5% is found for H//a. The magnetization exhibits a smooth increase at 2 K, reaching values of M(18T) = 0.03, 0.05, 0.17 mB/f.u. for H//a, H//b, and H//c, respectively. This anisotropy found in M(H) is consistent with that observed for Dr(H//a) > Dr(H//b) > Dr(H//c). These results can be interpreted in terms of the field-dependent scattering mechanism of CaVO3.
We report the results of ac and dc magnetic susceptibility (chi) and electrical resistivity (rho) measurements on the single crystals of Er2PdSi3, crystallizing in an AlB2-derived hexagonal structure, for two orientations H//[0001] and H//[2 -1 -1 0]. For H//[0001], there are apparently two magnetic transitions as revealed by the ac chi data, one close to 7 K attributable to antiferromagnetic ordering and the other around 2 K. However, for H // [2 -1 -1 0], we observe additional features above 7 K (near 11 and 23 K) in the plot of low-field chi(T); also, there is no corresponding anomaly in the rho(T) plot. In this respect, the magnetic behavior of this compound is novel, particularly while compared with other members of this series. The features in ac chi respond differently to the application of a small dc magnetic field for the two directions. As far as low temperature (T= 1.8 and 5 K) isothermal magnetization (M) behaviour is concerned, it exhibits meta-magnetic-like features around 2 kOe saturating at high fields for the former orientation, whereas for the latter, there is no saturation even at 120 kOe. The sign of paramagnetic Curie temperature is different for these two directions. Thus, there is a strong anisotropy in the magnetic behavior. However, interestingly, the rho(T) plots are found to be essentially isotropic, with the data revealing possible formation of magnetic superzone formation below 7 K.
We report temperature and thermal-cycling dependence of surface and bulk structures of double-layered perovskite Sr3Ru2O7 single crystals. The surface and bulk structures were investigated using low-energy electron diffraction (LEED) and single-crystal X-ray diffraction (XRD) techniques, respectively. Single-crystal XRD data is in good agreement with previous reports for the bulk structure with RuO6 octahedral rotation, which increases with decreasing temperature (~ 6.7(6)degrees at 300 K and ~ 8.1(2) degrees at 90 K). LEED results reveal that the octahedra at the surface are much more distorted with a higher rotation angle (~ 12 degrees between 300 and 80 K) and a slight tilt ((4.5pm2.5) degrees at 300 K and (2.5pm1.7) degrees at 80 K). While XRD data confirms temperature dependence of the unit cell height/width ratio (i.e. lattice parameter c divided by the average of parameters a and b) found in a prior neutron powder diffraction investigation, both bulk and surface structures display little change with thermal cycles between 300 and 80 K.
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