Heavy fermion behavior in Pr0.5Ir4Sb10.2Sn1.8

doi:10.1016/j.physb.2020.412428

Physica B: Condensed Matter

Volume 598, 1 December 2020, 412428

https://doi.org/10.1016/j.physb.2020.412428 Get rights and content

Highlights

•
First single crystal synthesis of new partially filled skutterudite, Pr0.5Ir4Sb10.2Sn1.8.
•
Characterization through specific heat, magnetization, and resistivity measurements from room temperature to 50 mK.
•
Kondo alloy behavior evidenced from low temperature fits to resistivity and specific heat.
•
A small superconducting fraction observed through transitions in resistivity and magnetization.

Abstract

We report on the properties of single crystals of Pr_0.5Ir₄Sb_10.2Sn_1.8, a new partially-filled rare earth skutterudite which exhibits Kondo alloy and heavy fermion behavior. Using magnetic susceptibility, specific heat, and resistivity measurements we find evidence of Kondo-screening of the f-moments. This material shows a Kadowaki-Woods ratio consistent with heavy fermion behavior. Susceptibility measurements predict a Kondo temperature $T_{K} \approx 4 K$ , however the minimum found in the low temperature resistivity appears at a higher temperature $T \approx 10 K$ . A small fraction of the material ( $< 0.5 %$ ) becomes superconducting with a critical temperature $T_{c} \approx 4.2 K$ .

Introduction

Filled skutterudites have attracted a great deal of interest for both their fundamental properties and potential applications. They exhibit a variety of interesting behaviors, including heavy fermion states [[1], [2], [3], [4]], anti-ferroquadrupolar order [5,6], non-Fermi liquid states [7,8], metal insulator transitions [9,10], and BCS [11,12] and exotic [13,14] superconductivity.

For thermoelectric applications, atoms in the voids of the skutterudite structure result in anharmonic vibrations with Einstein-like modes which can effectively scatter phonons [15]. This scattering does not substantially reduce the electrical conductivity, leading to a better thermoelectric figure of merit.

Pr filled skutterudites in particular have a variety of interesting ground states; For instance, PrFe₄P₁₂ shows a metal-insulator transition with anti-ferroquadrupolar ordering below the transition [16]. PrFe₄As₁₂ orders ferromagnetically at low temperatures [17], while PrRu₄As₁₂ is suggested to be an s-wave superconductor [18]. Perhaps the most interesting is PrOs₄Sb₁₂, an unconventional heavy fermion superconductor in which the pairing is thought to be odd parity and mediated by quadrupole fluctuations [19,20], which may host three dimensional Majorana fermions [21].

The large number of interesting behaviors for filled skutterudites has prompted attempts at synthesizing new compounds within this structural family. Luo et al. [22] looked at Group 9 skutterudites based on Co, Ru, and Ir. They showed that the filled skutterudites in these systems follow Zintl rules for formation, and by altering the atoms involved but keeping close to the same valence electron count (96), they were able to create more than 60 new compounds with hundreds more potentially possible. Based on electron counting rules, most of these materials should be close to a semiconducting state. The Ir members of this group are particularly interesting, since the large Z of Ir results in a strong spin-orbit coupling. By following these rules, partially filled skutterudites can also be created. Two of the compounds they synthesized in powder form were PrIr₄Sb₈Sn₄ and Pr_0.9Ir₄Sb_10.2Sn_1.8.

Here we report the creation and characterization of single crystal samples of Pr_0.5Ir₄Sb_10.2Sn_1.8. We determined the crystal structure and relative composition through powder x-ray diffraction (PXRD) and energy dispersive x-ray spectroscopy (EDS), and found interesting low temperature behavior through specific heat, magnetization and electronic transport measurements. This material displays Kondo-alloy and heavy fermion behavior.

Section snippets

Methods

We synthesized single crystal Pr_0.5Ir₄Sb_10.2Sn_1.8 using the self-flux method following Bauer et al. [13]. Praseodymium (ingot, 3 N), iridium (powder, 4 N), antimony (shot, 5 N) and tin (shot, 4 N) were weighed (atomic ratios 1:4:13.33:6.66) and then sealed in carbon coated quartz ampoules which had been evacuated and then filled with 500 millitorr of argon gas. The samples were grown in the temperature range of $950 {}^{\circ}C$ to $650 {}^{\circ}C$ with a $1 {}^{\circ}C / h r$ cooling rate and were then placed in a centrifuge at $650$

Crystallography and composition

Fig. 1 shows the PXRD pattern and Rietveld refinement of a powdered single crystal Pr_0.5Ir₄Sb_10.2Sn_1.8 sample. The peaks are well indexed by the LaFe₄P₁₂ type cubic structure with space group Im-3 (#204). There is one very small peak of impurity phase at $28^{\circ}$ which was unidentifiable, however did not consist of any elements or compounds which may have come from the crystal growth process. The refined lattice parameter is found to be $a = 9.2783 Å$ . This is comparable to the value given by Ref. [22]

Conclusions

In conclusion, we have grown the first single crystal samples of Pr_0.5Ir₄Sb_10.2Sn_1.8. This material shows heavy fermion behavior and Kondo like scattering. The large negative Curie temperature [ $θ_{W} = - 15.5 (5) K$ ] implies antiferromagnetic correlations and a Kondo temperature $T_{K} \approx 3.9 K$ . From the specific heat we find an enhanced electronic coefficient $γ = 29.4 m J / m o l K^{2}$ , which is on the lower extreme of a heavy fermion compound. The value for $γ$ , along with the $T^{2}$ coefficient $A$ extracted from the

CRediT authorship contribution statement

Matthew S. Cook: Investigation, Formal analysis, Visualization, Writing - original draft. Clement A. Burns: Conceptualization, Methodology, Investigation, Validation, Writing - review & editing, Supervision, Funding acquisition.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

We would like to thank Dr. Pnina Ari-Gur, Department of Mechanical and Aerospace Engineering, Western Michigan University for use of the PANalytical PXRD facility which was funded by National Science Foundation, United States MRI Award 1626276. This work was partially funded by Michigan Space Grant Consortium, NASA grant #NNX15AJ20H. The PPMS used for measurements was funded by NSF MRI grant 1828387.

References (60)

H. Sugawara et al.
Phys. Rev. B
(2002)
R. Gumeniuk et al.
New J. Phys.
(2010)
S. Sanada et al.
J. Phys. Soc. Jpn.
(2005)
D.A. Gajewski et al.
J. Phys. Condens. Matter
(1998)
M. Kohgi et al.
J. Phys. Soc. Jpn.
(2003)
J. Kikuchi et al.
Phys. B Condens. Matter
(2005)
R.E. Baumbach et al.
J. Phys. Condens. Matter
(2008)
M. Nicklas et al.
Phys. Rev. Lett.
(2012)
C. Sekine et al.
Phys. Rev. Lett.
(1997)
K. Matsuhira et al.
J. Phys. Soc. Jpn.
(2002)

I. Shirotani et al.

Phys. Rev. B

(1997)

E. Bauer et al.

Phys. Rev. Lett.

(2007)

E.D. Bauer et al.

Phys. Rev. B

(2002)

Y. Aoki et al.

Phys. Rev. Lett.

(2003)

D. Cao et al.

Phys. Rev. B

(2004)

Y. Aoki et al.

Phys. Rev. B

(2002)

T.A. Sayles et al.

Phys. Rev. B

(2008)

T. Namiki et al.

J. Phys. Soc. Jpn.

(2007)

M.B. Maple et al.

ArXiv:Cond-Mat/0303370

K. Miyake et al.

J. Phys. Condens. Matter

(2003)

V. Kozii et al.

Sci. Adv.

(2016)

H. Luo et al.

Nat. Commun.

(2015)

H.M. Rietveld

J. Appl. Crystallogr.

(1969)

T. Degen et al.

Powder Diffr.

(2014)

R. Mondal et al.

Phys. Rev. B

(2018)

B.K. Rai et al.

Phys. Rev. B

(2019)

J. Chen et al.

Sci. Rep.

(2017)

J.R. Clem et al.

Phys. Rev. B

(1993)

M. Rotter et al.

Phys. Rev. Lett.

(2008)

V. Sandu et al.

Phys. Rev. B

(2006)

Cited by (0)

View full text

Physica B: Condensed Matter

Heavy fermion behavior in Pr0.5Ir4Sb10.2Sn1.8

Highlights

Abstract

Introduction

Section snippets

Methods

Crystallography and composition

Conclusions

CRediT authorship contribution statement

Declaration of competing interest

Acknowledgements

Phys. Rev. B

New J. Phys.

J. Phys. Soc. Jpn.

J. Phys. Condens. Matter

J. Phys. Soc. Jpn.

Phys. B Condens. Matter

J. Phys. Condens. Matter

Phys. Rev. Lett.

Phys. Rev. Lett.

J. Phys. Soc. Jpn.

Phys. Rev. B

Phys. Rev. Lett.

Phys. Rev. B

Phys. Rev. Lett.

Phys. Rev. B

Phys. Rev. B

Phys. Rev. B

J. Phys. Soc. Jpn.

ArXiv:Cond-Mat/0303370

J. Phys. Condens. Matter

Sci. Adv.

Nat. Commun.

J. Appl. Crystallogr.

Powder Diffr.

Phys. Rev. B

Phys. Rev. B

Sci. Rep.

Phys. Rev. B

Phys. Rev. Lett.

Phys. Rev. B

Heavy fermion behavior in Pr_0.5Ir₄Sb_10.2Sn_1.8