Magnetic and physical properties of new hexagonal compounds PrPt_4X
(X = Ag, Au)
release_yvrqqh6qpjhyhbrv6x7xtsjule
by
Michael O Ogunbunmi, André M Strydom
2019
Abstract
We have synthesized PrPt_4Ag and PrPt_4Au compounds for the first time
and report their crystal structure, as well as magnetic and physical properties
in the temperature range of 1.9 K to 300 K. Both compounds are derived from the
substitution of Pt with Ag and Au, respectively in the parent compound PrPt_5
which crystallizes in the hexagonal CaCu_5-type structure. Here we observed
the preservation of the hexagonal CaCu_5-type structure under such
substitutions, which is in contrast to the observations in PrCu_4Ag and
PrCu_4Au adopting the cubic MgCu_4Sn-type structure upon substitution on
parent hexagonal PrCu_5. The temperature dependences of specific heat
C_p(T), and electrical resistivity ρ(T) of PrPt_4Ag show an anomaly at
7.6 K. This is absent in the magnetic susceptibility χ(T), thus suggesting
a possible multipolar ordering of the Pr^3+ moment. PrPt_4Au on the other
hand does not show any anomaly but an upturn in C_p(T)/T below about 10 K and
attains 1.23 J/(mol K^2) at 1.9 K. In addition, ρ(T) ∼ T for nearly
a decade in temperature. These observations for PrPt_4Au are the hallmark of
a non-Fermi liquid (nFL) behavior and is characteristic of a system near a
quantum critical point. The analyses of the low-temperature C_p(T) for
PrPt_4Ag and PrPt_4Au give values of the Sommerfeld coefficient, γ =
728.5 mJ/(mol K^2) and 509.1 mJ/(mol K^2), respectively, indicating a
significant enhancement of the quasiparticle mass in the two compounds.
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