Magnetic anisotropy and electronic transport properties in single-crystalline compounds of EuCu2Ge2 and EuCu2Si2

Abstract

We present the temperature dependent magnetization, M(T), and the resistivity, ρ(T), of EuCu2Ge2 and EuCu2Si2 in single crystalline form. The EuCu2Ge2, which is synthesized in single-crystalline form, shows two different magnetic transitions in M(T) at TMc=8.5 K and TMab=4 K depending upon the magnetic field orientation. On the other hand, the ρ(T) reveals only one transition at T=4 K as a sudden drop of the ρ(T) without any noticeable change at T=8.5 K. For the EuCu2Si2, M(T) shows a two step antiferromagnetic transition at TN1≈10 K and TN2≈4 K, which is smeared out under H⩾1 T, probably due to field induced spin orientation. The transition at TN2 is also manifested as a decrease in ρ(T) due to loss of magnetic scattering. Interestingly, another exotic transition is found at T=2 K in ρ(T) data. The ρ(T) values rapidly increase by two orders of magnitude from ρ=20 μΩ cm at T=2 K and reach ρ=5 mΩ cm at T=0.5 K, which is similar to a metal–insulator transition.

Absence of charge fluctuations of europium in metallic single crystals of EuCu2Si2

“…Single crystals of EuCu 2 Si 2 were synthesized from an In flux, as described in [7]. They were found to be single phase, crystallizing in the tetragonal ThCr 2 Si 2 structure with lattice constants a=4.10 Å and c=9.93 Å [7].…”

“…They were found to be single phase, crystallizing in the tetragonal ThCr 2 Si 2 structure with lattice constants a=4.10 Å and c=9.93 Å [7]. 151 Eu Mössbauer measurements were performed in the temperature range 2.2-299.5 K with a standard Mössbauer spectrometer operating in a sine mode using a 330 mCi 151 Sm (SmF 3 ) source kept at room temperature.…”

Self-flux growth of large EuCu2Si2 single crystals

“…Whereas the crystals grown from the indium flux fail to show these features and instead exhibit plain antiferromagnetism [7]. [7,8], where the axis orientation was not indicated. In contrast to the magnetic susceptibility, the anisotropy in the electrical resistivity for the two different crystallographic orientations is less significant.…”

“…Here the molten zone acts as a self-flux, which considerably differs from the In flux used by previous authors [7,8]. The magnetic and electronic transport properties of the grown crystals have been described in a previous article [10].…”

“…In Ref. [8] for crystals prepared with the same method two magnetic transitions at 10 and 4 K and exotic electrical properties below T¼2 K were reported. This behavior and the magnetic properties of the single crystals turned out to be at strong variance with those of polycrystalline samples, which do not show evidence of magnetic order [3].…”