Neutron scattering, magnetization, and Mössbauer measurements onEuPd2Si2

Abstract

We report the measurement of the dynamic magnetic susceptibility of an intermediate-valence Eu compound in inelastic neutron scattering experiments, namely, on a sample of EuPd2Si2 with enriched '"Eu. The most remarkable feature is an increase of the quasielastic linewidth with decreasing temperature, which is apparently a consequence of the well-known temperature-driven valence change. Moreover, at low temperatures a strong inelastic line is observed, which is interpreted as a multiplet transition within the Eu + configuration (J =0~J = 1). To check the quality of the sample, additional Mossbauer and magnetization measurements were performed. From these we conclude a fraction of approximately 6%%uo of the so-called "satellite" phase in our sample, which is ferromagnetic at low temperatures and whose effects can be separated consistently out of all of our data.

Valence instability of europium in EuCo2Si2

“…Such inhomogeneous mixed valence is surprising in a compound with crystal structure containing no inequivalent europium sites-but may be explained by local disorder. The same holds probably also for mixed-valent EuCu 2 Si 2 [44], EuPd 2 Si 2 [45] and EuIr 2 Si 2 [46], for which unexpected ferromagnetic-like phase transitions were observed at low temperatures and were interpreted to be due to a magnetic impurity. For EuIr 2 Si 2 , the magnetic ordering disappeared after thermal treatment [46].…”

“…For EuIr 2 Si 2 , the magnetic ordering disappeared after thermal treatment [46]. However, the transition temperatures which can be depicted from susceptibility versus temperature curves for our EuCo 2 Si 2 and for EuCu 2 Si 2 [44], EuPd 2 Si 2 [45] and EuIr 2 Si 2 [46] are different, so the ferromagnetic-like behaviour cannot be due to a contamination by a simple phase, like EuO or one of the europium silicides. An eventual candidate for such ferromagnetism would be another, unknown ternary compound in the Eu-M-Si system (M: transition metal), which would exhibit similar magnetic behaviour but different ordering temperatures for different transition metals.…”

Low-temperature properties and magnetic order ofEuZn2Sb2

“…Measurements were carried out at low ac frequencies and low excitation levels to avoid parasitic signal interferences and self-heating of the sample. The transport data were recorded in the temperature range 1.5 K to room temperature at magnetic fields in the range up to 5 T using a conventional 4 He cryostat equipped with a superconducting solenoid. The dc magnetization was measured with a commercial vibrating sample magnetometer ͑VSM͒ down to 1.5 K at magnetic fields in the range up to 12 T. The specific heat was measured with a conventional heat-pulse technique in the range 1.5 K to 30 K in magnetic fields up to 14 T. The thermal expansion, finally, was measured with a bespoke miniature dilatometer in a 14-T quantum design physical properties measurement system.…”

“…This is the reason why the properties of the intermediate-valent systems EuPd 2 Si 2 and EuNi 2 P 2 have attracted great scientific interest in the past. [1][2][3][4][5] Another feature of Eu-based compounds is the nature of magnetically ordered states. Here even tiny valence fluctuation rates may result in various anomalous properties.…”

Wave-vector dependence of intermultiplet transitions inEuBa2Cu3

“…The small value for EuPd 2 Si 2 is proposed to originate from the intermediate valence character of Eu ͑Eu 2.7ϩ ͒. 21 The energy separation between multiplets arises primarily from the free-ion contributions. However, even using the free-ion parameters for Eu:LaF 3 ͑Ref.…”