Evidence for a dimensionality crossover at the disappearance of magnetism in the Kondo lattice alloyCeCo1−xFexSi

Abstract

Structural, magnetic, and thermal measurements performed on CeCo 1−x Fe x Si alloys are reported. Three regions can be recognized: (i) Co rich (x 0.20) with a decreasing long-range antiferromagnetic order which vanishes at finite temperatures, (ii) an intermediate region (0.20 < x 0.30) showing a broad magnetic anomaly (C A ) in specific heat, and (iii) the nonmagnetic region progressively changing from a non-Fermi-liquid-type behavior towards a Fermi-liquid one as Fe concentration increases. The C A anomaly emerges as an incipient contribution above T N already at x = 0.10, which indicates that this contribution is related to short-range correlations likely of quasi-two-dimensional type. Both T N transition and C A anomaly are practically unaffected by an applied magnetic field up to B ≈ 10 T.

Strong magnetoelastic effect in CeCo1−xFexSi as Néel order is suppressed

“…This valence change may also explain the large negative thermal expansion coefficient observed at high field. The interpretation is supported by the evolution of the unit-cell volume with the Fe content which shows an important Ce volume decrease above x ∼ x c [7], in line with previous magnetization [10] and X-ray absorption spectroscopy [11] measurements where an important Ce valence change in CeFeSi relative to CeCoSi was reported.…”

“…In this work we present another system where notable and strong magnetostructural effects are observed. The intermetallic CeCo 1−x Fe x Si alloys show antiferromagnetic (AFM) ordering (T N = 8.8 K) in the stoichiometric limit (x=0) which weakens as the Fe content is increased [7]. The linear magnetostriction ∆L/L, on the other hand, increases with x approaching a maximum value of ∆L L (16T, 2K) = 3×10 −3 at about the critical concentration x c ≈ 0.23 where the magnetic order disappears.…”

Landau theory for magnetic and structural transitions in CeCo0.85Fe0.15Si

“…This leads to a suppression of the Néel transition and the development of a bump in a way that resembles a dimensional crossover from 3D to 2D magnetism [15]. The antiferromagnetism is completely suppressed [see figure 1(b)] for y 0.23 [14]. Interestingly, an anomaly in the specific heat at a temperature T A > T N was identified in [14] which was interpreted as an onset of large magnetic fluctuations in the paramagnetic phase near the Néel transition.…”

“…The antiferromagnetism is completely suppressed [see figure 1(b)] for y 0.23 [14]. Interestingly, an anomaly in the specific heat at a temperature T A > T N was identified in [14] which was interpreted as an onset of large magnetic fluctuations in the paramagnetic phase near the Néel transition.…”

“…As the concentration of Fe (y) increases, the Néel temperature T N , as deduced from the peak in the specific heat at the transition, decreases and the peak becomes weaker [see figure 1(a)]. The behavior of the specific heat [14] suggests a chemical pressure effect due to the substitution of Co by Fe. This leads to a suppression of the Néel transition and the development of a bump in a way that resembles a dimensional crossover from 3D to 2D magnetism [15].…”