Search

We investigate the magnetic and crystal electric field (CEF) states of the Kondo lattice system CeCuGa3 by muon spin relaxation (muSR), neutron diffraction, and inelastic neutron scattering (INS) measurements. A noncentrosymmetric BaNiSn3-type tetragonal crystal structure (space group I4mm) is inferred from x-ray as well as from neutron powder diffraction. The low-temperature magnetic susceptibility and heat capacity data show an anomaly near 2.3 - 2.5~K associated with long range magnetic ordering, which is further confirmed by muSR and neutron diffraction data. The neutron powder diffraction collected at 1.7 K shows the presence of magnetic Bragg peaks indexed by an incommensurate magnetic propagation vector k = (0.148, 0.148, 0) and the magnetic structure is best described by a longitudinal spin density wave with ordered moments lying in ab-plane. An analysis of the INS data based on a CEF model reveals the presence of two magnetic excitations near 4.5 meV and 6.9 meV. The magnetic heat capacity data suggest an overall CEF splitting of 20.7 meV, however the excitation between 20 and 30 meV is very broad and weak in our INS data, but could provide an evidence of CEF level in this energy range in agreement with the magnetic entropy. Our analysis of INS data based on the CEF-phonon model indicates that the two excitations at 4.5 meV and 6.9 meV have their origin in CEF-phonon coupling (i.e. splitting of one CEF peak into two peaks, called vibron), with an overall splitting of 28.16 meV, similar to the case of CeCuAl3 and CeAuAl3., 13 pages, 14 figures

The spin–glass behavior in the ferromagnetic phase of Tm 2 Cu 2 In was investigated by dc–, ac–magnetization, and non-equilibrium dynamics characterizations. An argon arc–melted polycrystalline sample of the compound of Tm 2 Cu 2 In was found to adopt the Mo 2 FeB 2 –type tetragonal structure (space group P 4 / m b m ). The temperature variation of dc–magnetization exhibits a ferromagnetic behavior with Curie temperature T C = 32.5 K. The zero field cooled (ZFC) and field cooled (FC) magnetic curves show the thermomagnetic irreversible behavior below T C . The field dependence of irreversible temperature follows the Almeida–Thouless line. The frequency and ac–driven field dependent anomalies in ac–susceptibility results indicate the existence of a spin–glass state in Tm 2 Cu 2 In . The time dependence of magnetization further supports the spin–glass behavior observed in Tm 2 Cu 2 In . The frequency dependence of the freezing temperature in the real part of ac–susceptibility has been analyzed on the basis of a power–law divergence and Vogel–Fulcher law. The obtained results reveal that Tm 2 Cu 2 In belongs to the ferromagnetic canonical spin–glass class of compounds.

We report the synthesis, crystal structure, and thermodynamic properties of the two binary laves phases Ce3Cu and Pr3Cu, which crystallize in the tetragonal I4/mmm (space group: 139). We have investigated the compounds using dc magnetic susceptibility χdc(T), ac magnetic susceptibility χac(T), isothermal magnetization M(B) and specific heat Cp(T) measurements. Both compounds show features of strong geometrical frustration, which is driven by the arrangement of the rare-earth ions on triangular lattice sites. Ce3Cu shows a phase transition at TN = 5 K and its M(B) at 2 K reveals the presence of a metamagnetic transition near 2 T. Pr3Cu, on the other hand, shows a spin-glass behaviour with a freezing temperature of Tf1 ≃ 12 K and with an irreversible behavior in zero-field-cooled (ZFC) and field-cooled (FC) χdc(T) below about 13 K. The real part of χac(T) reveals a frequency dependence of Tf. The result, however shows the presence of another frequency-dependent phase below Tf2 ≃ 9.35 K, a feature which signals a re-entrant spin-glass behaviour in the compound. Furthermore, the frequency dependence of Tf1 follows the Vogel-Fulcher law, with an activation energy Ea∕kB = 5.3 K. This observation along with the estimated relative shift in Tf1 per decade in frequency δTf = 0.0105, irreversible behaviour in ZFC-FC χdc(T) and a slow decay in thermo-remnant magnetization provide supports for the formation of a cluster spin-glass in Pr3Cu. In addition, we observe the enhancement of the Sommerfeld coefficient, γ in both compounds with values of 0.1892(5) J/(molCe K2) and 0.5078(1) J/(molPr K2). The estimation of the Sommerfeld-Wilson ratio WR yield values of 0.576 and 1.17 for Ce3Cu and Pr3Cu, respectively.

We report the structural, magnetic properties, and magnetocaloric effect of a new polycrystalline compound of $\mathrm{Tb_2Rh_3Ge}$. This present compound crystallizes with $\mathrm{Mg_2Ni_3Si}$-type of rhombohedral Laves phases (space group $R\overline{3}m$, hR18). The magnetic properties and magnetocaloric effect of the $\mathrm{Tb_2Rh_3Ge}$ is explored through dc-magnetization measurements. Temperature dependence of magnetization revealed that the compound exhibits ferromagnetic behavior with $T_C$$=$56 K. The field dependence of magnetization indicates that $\mathrm{Tb_2Rh_3Ge}$ is a soft ferromagnet. The obtained isothermal magnetic entropy changes ($\Delta S_m$), and refrigeration capacity (relative power cooling) for a change of magnetic field 0-9 T are 12.74 J/kg-K, and 497(680) J/kg respectively. The Arrott plots and universal curve of normalized $\Delta S_m$ indicate that this compound undergoes second order ferromagnetic phase transition