Magnetic ordering in Gd₂Fe₂Si₂C

Abstract

The intrinsic magnetism of Gd2Fe2Si2C has been investigated using magnetization and specific heat measurements. Gd2Fe2Si2C orders magnetically below 58 K, consistent with the de Gennes scaling observed for the remaining (heavy‐R) R2Fe2Si2C compounds.A second magnetic event at ∼38 K is also observed in the susceptibility and specific heat data which might signal a spin–reorientation transition. Field dependent magnetometry suggests that the magnetic structure of this compound is quite complex.

Determination of the magnetic structure of Gd2Fe2Si2C by Mössbauer spectroscopy and neutron diffraction

“…No magnetic splitting is observed above this temperature. It is clear from the use of a direct local probe of the Gd magnetic behaviour that the Néel temperature of Gd 2 Fe 2 Si 2 C is 39(1) K which matches the specific heat signal previously reported [4]. The strong signal at 58 K seen in ac-susceptibility data [4] does not come from the primary Gd 2 Fe 2 Si 2 C phase and must therefore be due to the presence of a minor ferromagnetic impurity, possibly the Gd 3 C phase identified in the previously reported x-ray diffraction pattern [4].…”

“…It is clear from the use of a direct local probe of the Gd magnetic behaviour that the Néel temperature of Gd 2 Fe 2 Si 2 C is 39(1) K which matches the specific heat signal previously reported [4]. The strong signal at 58 K seen in ac-susceptibility data [4] does not come from the primary Gd 2 Fe 2 Si 2 C phase and must therefore be due to the presence of a minor ferromagnetic impurity, possibly the Gd 3 C phase identified in the previously reported x-ray diffraction pattern [4]. However, since Gd 3 C is reported to have a Curie temperature around room temperature [16], if this is indeed the source of the ferromagnetic response seen at 58 K, the phase cannot be stoichiometric.…”

“…The temperature dependence of the hyperfine magnetic field at the 155 Gd site splitting is shown in figure 6. A simple fit to these data using a J = 7/2 Brillouin function, appropriate to the Gd 3+ 4f 7 S-state ionic configuration, yields a Néel specific heat signal previously reported [4]. The strong signal at 58 K seen in ac-susceptibility data [4] does not come from the primary Gd 2 Fe 2 Si 2 C phase and must therefore be due to the presence of a minor ferromagnetic impurity, possibly the Gd 3 C phase identified in the previously reported x-ray diffraction pattern [4].…”

“…The lattice parameters of Gd 2 Fe 2 Si 2 C obtained by refinement of the x-ray diffraction pattern obtained at 298 K and shown in [4] are given in table 1 and are in excellent agreement with the values reported by Paccard and Paccard [1]. Despite numerous attempts, we were unable to avoid the production of small amounts (estimated at less than 2 wt.% based on refinement of the x-ray diffraction pattern) of an impurity phase matching Gd 3 C [14] (reported as GdC 0.33 to reflect the observed range of Gd:C ratios).…”

“…The Néel temperature of Gd 2 Fe 2 Si 2 C was reported to be 9 K [2] which represents a spectacular failure of the de Gennes scaling, given that the Tb compound orders at 45 K. In a recent report on Gd 2 Fe 2 Si 2 C [4] two quite prominent magnetic signals in magnetometry and susceptibility measurements were observed at 38 K and 58 K although only the lower 'event' was observed in heat capacity measurements. The strong magnetic signal at 58 K was tentatively suggested to represent the magnetic ordering of Gd 2 Fe 2 Si 2 C.…”