Ce₃Cu₃Sb⁴: a Canted Antiferromagnetic Semimetal

Abstract

It has been claimed by Patil et al., Solid State Commun. 99, 419 (1996) that Ce3Cu3Sb4 is the first Ce-based semiconducting ferromagnet. In this paper it is shown, mainly with Hall effect and far infrared spectroscopy that no gap in the excitation spectrum exists, as well above as below the magnetic ordering temperature. A maximum in the resistivity near Ta is due to trapped magnetic polarons. The resistivity is an effect of the mobility of the charge carriers. The structure of the magnetic unit cell has been determined with elastic neutron scattering. ι PACS numbers: 72.15.Eb, 72.15.Gó

Thermodynamic properties and magnetism of Ce3Cu3Sb4

“…A few years ago Ce 3 Cu 3 Sb 4 was described as a ferromagnetic semiconductor [1,2] with a Curie temperature T trs of ≈10 K. Recently, further investigations on this material concentrated on the estimation of the performance in thermoelectric applications [3,4]. The ordered state of Ce 3 Cu 3 Sb 4 at low temperature, however, which in all previous investigations showed a spontaneous magnetic moment below T trs , remained a matter of debate [5,6]. Since the resistivity ρ(T ) showed a maximum at a certain temperature T max , which varied in the different studies and which did not coincide with T trs , and above which activated conduction was found, Ce 3 Cu 3 Sb 4 was classified as a degenerate p-type semiconductor [2,3].…”

“…Since the resistivity ρ(T ) showed a maximum at a certain temperature T max , which varied in the different studies and which did not coincide with T trs , and above which activated conduction was found, Ce 3 Cu 3 Sb 4 was classified as a degenerate p-type semiconductor [2,3]. The values calculated for the activation energy E A at high temperature are very small (E A /k B = 30 K [3]; 38 K [4]; 29 K [5,6]), but are remarkably consistent among the various authors. Below T max the resistivity decreases, but until now no clear temperature dependence could be identified.…”

“…It was argued [5,6] that it is unreasonable to discuss such small semiconductor gap values in an imperfect intermetallic compound. Also, a study of the substitution series Ce 3 Cu x Pt 3−x Sb 4 demonstrated that the gap almost closes when approaching x = 3 [4].…”

“…Also, a study of the substitution series Ce 3 Cu x Pt 3−x Sb 4 demonstrated that the gap almost closes when approaching x = 3 [4]. Since the optical reflectivity of Ce 3 Cu 3 Sb 4 shows no indication of a gap (reflectivity approaches 100% for ω → 0) [5,6], Ce 3 Cu 3 Sb 4 can rather be described as a semimetal. The temperature variation of ρ was ascribed to the temperature dependence of the mobility as established from Halleffect data [5,6].…”

“…Since the optical reflectivity of Ce 3 Cu 3 Sb 4 shows no indication of a gap (reflectivity approaches 100% for ω → 0) [5,6], Ce 3 Cu 3 Sb 4 can rather be described as a semimetal. The temperature variation of ρ was ascribed to the temperature dependence of the mobility as established from Halleffect data [5,6]. A description of Ce 3 Cu 3 Sb 4 as 'zero-gap semiconductor' [7] as given for the isostructural and isoelectronic Ce 3 Au 3 Sb 4 might also be adequate.…”