Anomalous susceptibility in single crystals of EuCo₂Si₂ with trivalent Eu: Influence of excited J multiplets

Abstract

We present a detailed study on the physical properties of single crystals of the Eu 3þ intermetallic EuCo 2 Si 2 . The Eu valence was confirmed by X-ray absorption. At low temperatures, the anisotropic susceptibility can be explained by a Eu 3þ Van Vleck contribution with a crystal field parameter V 0 2 ¼ 355 K, but at high temperatures the data exceed the Van Vleck values significantly. This excess susceptibility is possibly related to the magnetic exchange between the excited Eu multiplets and the conduction band. A g of 9.6 mJ K À2 mol and a Debye temperature of 322 K were estimated from the low temperature specific heat data. The compound does not undergo any phase transition in the temperature range 2-300 K.

Charge, lattice and magnetism across the valence crossover in EuIr2Si2 single crystals

“…This value of γ is higher than for the stable-valent compounds (9.6 mJ/K 2 mol for EuCo 2 Si 2 [12], ∼25 mJ/K 2 mol for EuRh 2 Si 2 [10]), indicating a moderate renormalization of the effective mass in agreement with optical spectroscopy studies [11]. The Debye temperature is much smaller than for the stablevalent compounds (388 K for EuRh 2 Si 2 [26], 332 K for EuCo 2 Si 2 [12]). Though a smaller Θ D is expected due to the higher mass of iridium atoms, the large thermal expansion in figure 2(a) suggests that the low value of Θ D for EuIr 2 Si 2 is related to the phonon softening induced by valence fluctuations.…”

“…At low temperatures, the specific heat of EuIr 2 Si 2 behaves as expected for a Fermi liquid, with an electronic contribution linear in temperature given by the Sommerfeld coefficient γ=33 mJ/K 2 mol, and a phonon contribution characterized by a Debye temperature Θ D =270 K [10]. This value of γ is higher than for the stable-valent compounds (9.6 mJ/K 2 mol for EuCo 2 Si 2 [12], ∼25 mJ/K 2 mol for EuRh 2 Si 2 [10]), indicating a moderate renormalization of the effective mass in agreement with optical spectroscopy studies [11]. The Debye temperature is much smaller than for the stablevalent compounds (388 K for EuRh 2 Si 2 [26], 332 K for EuCo 2 Si 2 [12]).…”

“…Single crystals of EuT 2 Si 2 were grown by a flux method (M =Rh,Ir) [10] or by a Bridgman technique (M =Co) [12] starting from high purity elements. Temperaturedependent synchrotron powder diffraction data on crushed single crystals were collected in transmission (Debye-Scherrer) geometry at the high-resolution beamline (ID22) of the European Syncrothron Radiation Facility (particle size < 32 µm, capillary of 0.3 mm diameter, λ = 0.400737(6) Å, 3 • ≤ 2θ ≤ 52 • , step 2θ = 0.002 • , multi-channel detector, 10 K ≤ T ≤ 293 K, liquid-helium cryostat).…”

Eu5Al3Sb6: Al4 Tetrahedra Embedded in a Rock-Salt-Like Structure

“…The fitting yields γ = 0.17(2) J mol −1 K −2 and β = 1.85(1) J mol −1 K −4 . The Sommerfeld coefficient γ per mol of Eu is 34 (4) mJ mol −1 K −2 , which is moderately higher than those of some stable-valent Eu compounds (EuCo 2 Si 2 39 with 9.6 mJ mol −1 K −2 and EuRh 2 Si 2 40 with 25 mJ mol −1 K −2 ) and comparable to those of Eu compound with valence fluctuations (EuIr 2 Si 2 41 with 33 mJ mol −1 K −2 ). Lower temperature data are needed to obtain a more precise value of γ.…”

Controlling magnetism via transition metal exchange in the series of intermetallics Eu(T1,T2)5In (T = Cu, Ag, Au)

“…Within this compound family, representatives with europium are particularly interesting because of the element's ability to adopt both +II and +III oxidation states as well as intermediate between +II and +III and, consequently, form compounds analogous to either rare earth or alkaline earth metals. [2][3][4] As a result, Eu intermetallics present both the diverse structural chemistry and fascinating magnetic properties. Interestingly both, chemical and physical pressure, have a considerable influence on the oxidation state of Eu and, hence, on the magnetic properties of Eucontaining compounds.…”