F. Kneidinger | Searcharxiv

arXiv2019

Physical properties of CeIrSi with trillium-lattice frustrated magnetism

Magnetic ($χ$), transport ($ρ$) and heat capacity ($C_m$)properties of CeIrSi are investigated to elucidate the effect of geometric frustration in this compound with trillium type structure because, notwithstanding its robust effective moment, $μ_{\rm eff}\approx 2.46μ_B$, this Ce-lattice compound does not undergo a magnetic transition. In spite of that it shows broad $C_m(T)/T$ and $χ(T)$ maxima centered at $T_{max}\approx 1.5$\,K, while a $ρ\propto T^2$ thermal dependence, characteristic of electronic spin coherent fluctuations, is observed below $T_{coh} \approx 2.5$\,K. Magnetic field does not affect significantly the position of the mentioned maxima up to $\approx 1$\,T, though $χ(T)$ shows an incipient structure that completely vanishes at $μ_0 H \approx 1$\,T. Concerning the $ρ\propto T^2$ dependence, it is practically not affected by magnetic field up to $μ_0 H = 9$\,T, with the residual resistivity $ρ_0(H)$ slightly decreasing and $T_{coh}(H)$ increasing. These results are compared with the physical properties observed in other frustrated intermetallic compounds

cond-mat.str-el↗

arXiv2017

Clathrate formation in the systems Sr-Cu-Ge and {Ba,Sr}-Cu-Ge

In the ternary system Sr-Cu-Ge, a clathrate type-I phase, Sr8Cu5.3Ge40.7 (a = 1.06311(3), exists close to the Zintl limit in a small temperature interval. Sr8Cu5.3Ge40.7 decomposes eutectoidally on cooling at 730°C into (Ge), SrGe2 and tau1-SrCu2-xGe2+x. Phase equilibria at 700°C have been established for the Ge rich part and are characterized by the appearance of only one ternary compound, tau1-SrCu2-xGe2+x, which crystallizes with the ThCr2Si2 structure type and forms a homogeneity range up to x=0.4 (a = 0.42850(4), c = 1.0370(1) nm). Additionally, the extent of the clathrate type-I solid solution Ba8-xSrxCuyGe46-y (5.2 < y < 5.4) has been studied at various temperatures. The clathrate type-I crystal structure (space group ) has been proven by X-ray single crystal diffraction on two single crystals with composition Sr8Cu5.3Ge40.7 (a = 1.06368(2) nm) and Ba4.9Sr3.1Cu5.3Ge40.7 (a = 1.06748(2) nm) measured at 300, 200 and 100 K. From the temperature dependency of the lattice parameters and the atomic displacement parameters, the thermal expansion coefficients, the Debye- and Einstein-temperatures and the speed of sound have been determined. From heat capacity measurements of Sr8Cu5.3Ge40.7 at low temperatures, the Sommerfeld coefficient and the Debye temperature have been extracted, whereas from a detailed analysis of these data at higher temperatures, Einstein branches of the phonon dispersion relation have been derived and compared with those obtained from the atomic displacement parameters. Electrical resistivity measurements of Sr8Cu5.3Ge40.7 reveal a rather metallic behaviour in the low temperature range (< 300 K).

cond-mat.mtrl-sci↗