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Abstract:
The robust field-insensitive heavy fermion features in Sm-3 Ru-4 Ge-13
and the magnetic phase transition at T-N approximate to 5 K are studied
using magnetization M(T), specific heat C-p(T), resistivity rho(T) and
thermal conductivity k(T)(T). The average crystal structure of Sm-3 Ru-4
Ge-13 conforms to the cubic space group Pm (3) over barn however,
signatures of subtle structural distortions are obtained from the x ray
data. The magnetic susceptibility, chi(T), follows a modified
CurieeWeiss law indicating the presence of crystal fields of Sm3+ and
the significance of van Vleck terms. No sign of ferromagnetism is
observed in M(H) of Sm-3 Ru-4 Ge-13 which yields only 0.025
mu(B)/f.u.-Sm at 2 K, 7 T. The Sommerfeld coefficient, gamma approximate
to 220 mJ/mol-Sm K-2, estimated from the analysis of low temperature
specific heat suggests the formation of heavy quasi particles at low
temperature. Though a lnT dependence of rho(T) is observed till 60 K,
the resistivity behavior is accounted for by assuming a two-band model
for activated behavior of charge carriers. The field scans of
resistivity, rho(H), below TN display significant nonlinearity while
those above the TN are more metal-like. Low values of thermal
conductivity, kappa(T)(T), are observed in Sm-3 Ru-4 Ge-13 however,
displaying an anomaly at T-N which signifies magnetoelastic coupling. A
fairly high value of Seebeck coefficient, S approximate to 40 mu V/K is
observed at 300 K. We identify Sm-3 Ru-4 Ge-13 as a low charge carrier
density system with unusual field-insensitive heavy fermion features
very similar to the filled skutterudites. (C) 2016 Elsevier B.V. All
rights reserved.
