Possibility of a new order parameter driven by multipolar moment and Fermi surface evolution in CeGe

Abstract

Polycrystalline CeGe is investigated by means of DC and AC susceptibility, non-linear DC susceptibility, electrical transport and heat capacity measurements in the low temperature regime. This compound shows two peaks at low magnetic field around TI ~ 10.7 and TII ~ 7.3 K due to antiferromagnetic ordering and subsequent spin rearrangement respectively. Investigation of non-linear DC susceptibility reveals a presence of higher order magnetization which results in the development of a new order parameter around TI. This leads to a lowering of symmetry of the magnetic state. The order parameter increases with decreasing temperature and stabilizes around TII. Consequently, the symmetry of the magnetic state is preserved below this transition. Heat capacity and resistivity results indicate the presence of a gap opening around TI on portion of Fermi surface, due to evolution of the Fermi surface. Magnetoresistance behavior and violation of Kohler’s rule suggest that the evolution of Fermi surface changes the symmetry of magnetic state. The observation of new order parameter (which is of second order) is also confirmed from the Landau free energy theory.

Molecular Network Approach to Anisotropic Ising Lattices: Parsing Magnetization Dynamics in Er3+ Systems with 0–3-Dimensional Spin Interactivity

“…Now, let us further examine the curious features of the two susceptibility peaks in our data, coupled to the transitions seen in isothermal magnetization hysteresis loops. The presence of multiple susceptibility peaks and field-dependent susceptibility events have been discussed in the solid-state literature for CeGe, lanthanide-containing double perovskites, Gd/TbAuAl 4 Ge 2 , and others. ,,− Most works discuss these kinds of anomalous events as magnetic phase transitions with long-range ordering and the potential presence of spin rearrangement or polarizability. Consistently, these multiple peaks are assigned as Neel temperatures and attributed to phase transitions occurring within the compound.…”

“…Revealing this behavior, however, requires nonstandard measurements and analysis for SMMs, such as the study of the demagnetization curvature, virgin curve analysis, and low-field susceptibility measurements. The precedence for long-range coupling of highly anisotropic spin centers has a rich history of study in the solid-state physics magnetism community, where the presence of multiple susceptibility peaks is used to detect potential spin-flop, spin-flip, or metamagnetic phase transitions. − Given the many intrinsic similarities between molecular crystals of lanthanide single-ion SMMs and solid-state anisotropy-driven magnetic materials, the isothermal virgin magnetization curves from H = 0–7 T at T = 2–12, 20 K (Figures B,C and S16, S24, and S35) were collected. These data, in connection with the high degree of anisotropy of the [ErCOT 2 ] anionic dipolar spin network, confirm the presence of a metamagnetic spin-flip transition in all of our compounds below their 10 K blocking temperature.…”

Evidence of charge susceptibility and multiple f–c hybridization configurations with the La doping in CeGe: a DFT + DMFT study

“…In this respect, we probe a magnetically diluted Ce-based system, Ce 0.6 La 0.4 Ge. This compound undergoes antiferromagnetic magnetic transition around 4.7 K, which is lower than ∼10.7 K, reported for the parent CeGe [33,34]. CeGe crystallizes in the orthorhombic structure with space group Pnma, which contains four Ce-sites per unit cell.…”

“…The two end members are categorized as CeGe and Ce 0.24 La 0.76 Ge based on their magnetization and the effect of f -c hybridization. In both these compounds, CeGe has stronger local moment character and f -c hybridization, while for Ce 0.24 La 0.76 Ge it is the opposite [33,34]. Further, in both cases, the presence of charge fluctuations and associated phenomena are obscured either by strong or weak hybridization.…”

“…Substitution of La reduces the net magnetic moments per unit cell which might help probe other hidden properties, particularly in Ce 0.6 La 0.4 Ge. The parent compound CeGe has a strong local moment character and f -c hybridization, which allows a long-ranged magnetically ordered state [33]. With La substitution, this magnetic ordering temperature decreases and possibly drops down to zero in Ce 0.24 La 0.76 Ge, where the local moment and hybridization effect becomes weaker [34].…”