Magnetic ordering in Ho2Fe2Si2C

Abstract

We have used neutron diffraction and 57Fe Mössbauer spectroscopy, complemented by magnetisation and specific heat measurements, to examine the magnetic ordering of Ho2Fe2Si2C. We have established that Ho2Fe2Si2C orders antiferromagnetically below TN = 16(1) K with a magnetic structure involving ordering of the Ho sublattice along the b-axis with a propagation vector k=[0 0 12]. 57Fe Mössbauer spectra collected below TN show no evidence of a magnetic splitting, demonstrating the absence of long range magnetic ordering of the Fe sublattice. A small line broadening is observed in the 57Fe spectra below TN, which is due to a transferred hyperfine field—estimated to be around 0.3 T at 10 K—from the Ho sublattice.

Magnetic structure and spin reorientation of quaternary Dy2Fe2Si2C

“…Based on 57 Fe Mössbauer spectroscopy measurements, the Fe atom was found to be non-magnetic in these compounds [8][9][10]. In addition, we observed a large spontaneous magnetostriction in Tb 2 Fe 2 Si 2 C below the antiferromagnetic transition [10] which suggests the existence of a correlation between the lattice and the ordered moment in the R 2 Fe 2 Si 2 C series.…”

“…The best refinement to the diffraction pattern at 16 K is obtained using the Γ 4 representation with the ordering of the Dy magnetic moment along the b-axis, similar to the cases of Gd 2 Fe 2 Si 2 C [9], Tb 2 Fe 2 Si 2 C [10] and Ho 2 Fe 2 Si 2 C [8]. The refined Dy moment at 16 K is 6.6(1) µ B with the refinement parameters for the 16 K pattern shown in table 2.…”

“…Such a scenario, however, cannot be expected in the R 2 Fe 2 Si 2 C series where the Fe sublattice is non-magnetic which suggests that crystal field effects are responsible for the spin-reorientation process. In Tb 2 Fe 2 Si 2 C and Ho 2 Fe 2 Si 2 C, the R magnetic moment is aligned along the b-axis and no spin-reorientation is observed down to 3 K [8,10]. Given that the Tb 3+ , Dy 3+ and Ho 3+ ions have a negative second-order Stevens coefficient [20], the direction of the Dy magnetic moment in Dy 2 Fe 2 Si 2 C is not dictated by the second-order crystal field term, and the occurrence of a spinreorientation in this compound-in contrast to Tb 2 Fe 2 Si 2 C and Ho 2 Fe 2 Si 2 C-is likely to be driven by the competition between the second-, fourth-and sixth-order crystal field terms acting on the Dy 3+ ion.…”

Effects of Y and Lu substitutions on the low temperature structural properties of Tb2Fe2Si2C

“…Recent neutron diffraction studies show that the common magnetic structure of the heavy-R2Fe2Si2C compounds are characterized by a propagation vector k = [0, 0, ½] with the R magnetic moments point along the b-axis [4][5][6]. 57 Fe Mössbauer spectroscopy studies revealed that the Fe carries no magnetic moment in this series of compounds [4][5][6].…”