EuNiGe₃, an anisotropic antiferromagnet

Abstract

Single crystals of EuNiGe3, crystallizing in the non-centrosymmetric BaNiSn3-type structure, were grown using In flux, enabling us to explore the anisotropic magnetic properties, which was not possible with previously reported polycrystalline samples. The EuNiGe3 single crystalline sample is found to order antiferromagnetically at 13.2 K, as revealed from the magnetic susceptibility, heat capacity and electrical resistivity data. The low temperature magnetization M (H) is distinctly different for the field parallel to the ab-plane and c-axis; the ab-plane magnetization varies almost linearly with the field before the occurrence of an induced ferromagnetic (FM) phase (spin-flip) at 6.2 Tesla. On the other hand M (H) along the c-axis is accompanied by two metamagnetic transitions followed by a spin-flip at 4.1 T. A model including anisotropic exchange and dipole-dipole interactions reproduces the main features of magnetization plots but falls short of full representation. (H,T) phase diagrams have been constructed for the field applied along the principal directions. From the (151)Eu Mössbauer spectra, we determine that the 13.2 K transition leads to an incommensurate antiferromagnetic (AFM) intermediate phase followed by a transition near 10.5 K to a commensurate AFM configuration.

Exploring metamagnetism of single crystallineEuNiGe3by neutron scattering

“…Figure 4 top shows that, up to 12 K, the thermal variation of the scattering intensity can be well fitted to the S=7/2 mean field function adequate for Eu 2+ ions, with a molecular field constant |λ| 5.95 T/µ B . Such a fit gives an excellent agreement between calculated and experimental data, with a transition tem- perature T t 12.0 K. Above 11 K, the (1+δ 1 /4 1) satellite intensity deviates from the mean field function, and vanishes above 13.5 K. In this temperature range, the observed small shift of the δ value corresponds to the intermediate phase reported in the Mössbauer investigation 15 , which shows an incommensurate modulation of Eu moments. Therefore, the value δ =0.066 does correspond to an incommensurate modulation, but the weakness of the magnetic signal in this phase prevented us from determining its detailed structure.…”

“…15. For the neutron diffraction study, a 3x3.7x1 mm 3 single crystal was mounted with the c axis or the b axis vertical in the variable temperature insert of a 7.5 T split-coil cryomagnet.…”

“…It crystallizes in a body-centered tetragonal structure (space group I4mm) and presents two magnetic transitions, at T N1 =13.2 K from the paramagnetic phase to an in- commensurate moment modulated phase, then at T N2 =10.5 K to an equal moment antiferromagnetic (AF) phase. The single crystal magnetization curve with field applied along the tetragonal c axis shows a particularly complex behavior at 1.8 K 15 , with two spin-flop like magnetization jumps at 2 and 3 T followed by a saturation in the field induced ferromagnetic phase at 4 T (see Fig.1). When the field is applied along the a (b) axis, the magnetization curve shows no such anomaly and reaches saturation at 6 T. However, a small deviation from linearity is observed for this direction at low field, as shown in the insert of Fig.1, and the linear behaviour is recovered above 1.3 T.…”

Direct and indirect measurements on electrocaloric effect: Recent developments and perspectives

“…33 While very similar concerns about the magnetic order parameters in antiferromagnetics were raised by Gschneidner et al, 44 treating the measured magnetization as the primary order parameter is frequently used in the magnetocaloric community. [45][46][47][48][49][50][51][52] It seems that the indirect method might still yield reasonable estimations about direct measurement results. For instance, it was reported that the direct measurement results in FeRh compounds can be well reproduced by the indirect method based on the magnetization measurements.…”

Low-Temperature Physical Properties of Single-Crystalline EuCoGe3and EuRhGe3

“…In the rst literature report [10], based on polycrystalline data, the compound was described as a simple A-type collinear antiferromagnet with T N = 13.6 K. However, in the most recent study on single crystals [11] In this contribution, we report on the low-temperature physical behaviours in the two novel representatives of the EuTGe 3 series, namely EuCoGe 3 and EuRhGe 3 .…”