Electronic and magnetic properties of quasi-skutterudite PrCo2Ga8 compound

Abstract

PrCo 2 Ga 8 is an orthorhombic quasi-skutterudite type compound which crystallizes in the CaCo 2 Al 8 structure type, with space group P bam (No. 55). The Pr 3+ ion has a site symmetry of C s which predicts a crystal electric field (CEF) level splitting into 9 singlets for J = 4. However, a phase transition at T m = 1.28 K is observed in electrical resistivity and specific heat results and is reported in this paper. The electrical resistivity shows an upturn below T m due to the superzone-gap formation. This transition is tuneable in fields and is suppressed to lower temperatures with applied magnetic fields. The electronic specific heat C p (T )/T increases below T m and reaches a value of 7.37 J/(mol K 2 ) at 0.4 K. The Sommerfeld coefficient, γ extracted from the low temperature analysis of C 4f (T )/T is 637 mJ/(mol K 2 ) indicating a possible mass enhancement of the quasiparticles. The calculated entropy value of 3.05 J/(mol K) is recovered around T m exhibiting almost 53% of Rln2, where R is the universal gas constant. Magnetic susceptibility results obeys the Curie-Weiss law for data above 100 K with an estimated effective magnetic moment, µ eff = 3.37 µ B /Pr and Weiss temperature, θ p = −124 K.

Superzone Gap Formation and Possible Kondo-like Features in the Heavy Fermion PrFe2Ga8 Compound

“…+ 1) µ B = 3.58 µ B for a free Pr 3+ ion and shows that Pr is the dominant magnetic species in the compound. The negative and large value of θ P confirms a predominant antiferromagnetic (AFM) interaction as well as the strength of interaction in the system similar to the observations in CeCo 2 Al 8 , PrCo 2 Ga 8 and LaFe 2 Al 8 where values of θ P = −136 K, −124 K and −285 K are reported, respectively[1,2,4].In the inset ofFig. 2(b), the isotherms, M(B) of PrFe 2 Ga 8 at 2 K and 20 K are shown.…”

“…A polycrystalline sample of PrFe 2 Ga 8 was prepared by arc melting stoichiometric amounts of high-purity elements (≥ 99.9 wt.%) in an Edmund Bühler arc melting furnace by a method described in ref. [2]. Powder X-ray diffraction spectra collected on a Rigaku SmartLab diffractometer at room temperature lend support to the Pbam space group crystal structure and no impurity phases were detected within the resolution limit of the instrument used.…”

“…The intermetallic compounds of the RT 2 X 8 family (R = rare earth, T = transition metal, X = Al, Ga, In) are caged structures that have been studied especially among the R = Ce compounds where physical properties ranging from intermediate valence to various forms of cooperative magnetism have been observed [1,2]. While several studies focused on Ce-based 1:2:8 compounds with connection to heavy fermion physics, little attention has so far been paid to the study of electronic and magnetic properties of Pr-based compounds in the same class.…”

Magnetic and physical properties of new hexagonal compounds PrPt$_4X$ ($X$ = Ag, Au)

“…From the fits, γ = 728.50 J/(mol K 2 ) and 509.10 J/(mol K 2 ) are obtained for PrPt 4 Ag and PrPt 4 Au, respectively. The observed γ values for these two compounds are more than two orders of magnitude greater than what is expected for an ordinary metal and qualitatively similar to those of the heavy fermion (HF) systems, where significant enhancement of the quasiparticles mass have been observed [13].…”

Investigation of the magnetic ground state of PrRu$_2$Ga$_8$ compound

“…The Sommerfeld coefficient γ has a direct relationship with the mass of the quasiparticles in a metal at low temperatures and it gives an idea about their degree of mass enhancement. We note that in a similar iso-structural compound PrCo 2 Ga 8 [14], an enhanced quasi-particle mass behaviour has been observed while on the other hand, iso-structural aluminides compounds like PrFe 2 Al 8 and PrCo 2 Al 8 [3,13] have been reported to have γ values in the range of ordinary metals (≈ 10 mJ/mol.K 2 ).…”