Magnetic behavior of bulk and fine particles of RCr₂Si₂C (R = La, Ce) compounds: possible magnetic ordering from Cr

Abstract

The magnetic behavior of the quaternary compounds, RCr(2)Si(2)C (R = La, Ce), has been investigated by magnetization (M) and heat-capacity (C) measurements (1.8-300 K) in the bulk polycrystals and nano forms (<1 µm) obtained by high-energy balling. Our finding is that Cr appears to exhibit magnetic ordering of an itinerant type at low temperatures (<20 K) in the bulk form, as inferred from a combined look at all the data. The magnetic ordering gets gradually suppressed with increasing milling time. Evidence for a mixed-valence state of Ce for the bulk form is obtained from the tendency of magnetic susceptibility to exhibit a maximum above 300 K. However, this feature vanishes in the nano form, which exhibits a Curie-Weiss behavior above 200 K as though Ce tends towards trivalency in these fine particles; in addition, there is a weak upturn in C/T below 10 K in the bulk, which becomes very prominent in the milled Ce-based specimens at lower temperatures, as though heavy-fermion behavior gets stronger in smaller particles.

Magnetic ordering in Gd2Fe2Si2C

“…The addition of carbon into RCr 2 Si 2 stabilizes the new RCr 2 Si 2 C compounds with the CeMg 2 Si 2 ‐type structure ( P 4/ mmm space group), another variant of the ThCr 2 Si 2 ‐type structure. These compounds have attracted significant attention in recent years, with particular interest aimed at understanding the magnetism of the Cr sublattice . In several reports, the Cr ion was reported to be magnetic , while other reports mainly from the single crystal magnetization and neutron diffraction studies exclude the possibility of the magnetic ordering of the Cr atom .…”

Observation of ferromagnetism in CeCr2Si2C single crystals

“…We attribute such low magnetic moment to the itinerant magnetism as that in LaCr 2 Si 2 C suggested by Mukherjee et al . 13 CeC 2 impurity-induced anomalous magnetic behavior with a transition temperature of 35 K was observed in polycrystalline CeCr 2 Si 2 C. 9 Our FM transition temperature (∼12.4 K) is significantly different from their results (35 K), eliminating the possibility of CeC 2 impurity-induced FM. Different from the results reported above, we observed a native FM behavior with a transition temperature of ∼12.4 K in CeCr 2 Si 2 C bulk single crystals, which is the first time observed FM in CeCr 2 Si 2 C with high purity.…”

“…For instance, CeCr 2 Si 2 C powders are found to show small spontaneous magnetization from the Cr sublattice below 30 K. 12 Instead, Pauli paramagnetic behavior linked to the intermediate-valence state of Ce is observed. 9 By adjusting the particle size, magnetic ordering originating from Cr is confirmed in CeCr 2 Si 2 C. 13 The inability to verify the properties, especially magnetism of CeCr 2 Si 2 C, limits the study of other potential behaviors such as superconductivity. To remove the effect of grain boundaries, secondary phases, and grain size on the magnetic properties and obtain native behaviors, high-quality single-bulk crystals are highly desired.…”

ThCr2Si2C: An Antiferromagnetic Metal with a Cr2C Square Lattice

“…As shown in Figure 2, the lattice parameters of LnCr 2 Si 2 C compounds expand with the ionic radius of Ln 3+ , except for the CeCr 2 Si 2 C where cerium shows a mixed-valent state. [15][16][17][18][19]23 For ThCr 2 Si 2 C, the ionic radius of Th 4+ is close to that of the Gd 3+ . This is consistent with the c-axis plotted in Figure 2.…”