Single Crystal Growth and Low Temperature Properties of PrNb₂Al₂₀

Abstract

Magnetization, electrical resistivity and specific heat measurements were performed on single crystals of PrNb 2 Al 20 grown by Al self-flux method. No evident anomalies suggesting phase transitions has been found down to 0.6 K. In all measurements, there appear features indicative of crystalline electric field levels with the energy splitting of ∼ 50 K. The monotonically increasing M-H curve at 2 K suggests a nonmagnetic Γ 1 singlet or a non-Kramers Γ 3 doublet ground state. In addition, low-lying excitations in 4 f -electron system remain down to 2 K remain and the associated features (a low temperature upturn in C/T and a non-Fermi liquid behavior in ρ) are observed.

Nonmagnetic ground state in the cubic compoundsPrNi2Cd20andPrPd2Cd20

“…Non-Fermi liquid behavior was observed for the isostructural heavy-fermion compound PrNb 2 Al 20 with a Γ 3 doublet ground state which is related to the quadrupole degrees of freedom. 25 Further experiments are needed to unambiguously identify the ground state of these new PrM 2 Cd 20 (M = Ni, Pd) compounds. Measurements of the magnetic field dependence of the low-temperature specific heat are in progress.…”

“…One of the important features of the PrM 2 X 20 compounds is that, in most cases, the Γ 3 doublet is considered to be the ground state. 18,21,22,25 Indeed, a recent inelastic neutron scattering study 23 and ultrasonic velocity measurements 26 have confirmed that the Γ 3 doublet is the ground state in PrTi 2 Al 20 and PrIr 2 Zn 20 . Recently, we succeeded in synthesizing RM 2 Cd 20 (R = rare earth; M = Ni, Pd) compounds in single crystalline form.…”

“…[17][18][19][20][21][22][23][24][25] In a cubic CEF, the J = 4 multiplet of the Pr 3+ ion splits into four levels: a Γ 1 singlet, a Γ 3 non-Kramers doublet, and Γ 4 and Γ 5 triplets. One of the important features of the PrM 2 X 20 compounds is that, in most cases, the Γ 3 doublet is considered to be the ground state.…”

“…27 Systematic studies of the structural, magnetic, electrical transport, and thermodynamic properties of the RM 2 Cd 20 family were recently published. 27,28 Since all of the known PrM 2 X 20 (X = Al, Zn) compounds are heavy fermion materials, [17][18][19][20][21][22][23][24][25] we were motivated to study these X = Cd compounds to ascertain whether they also exhibit strong electronic correlations or multipolar order.…”

Multipole and superconducting state in PrIr2Zn20probed by muon spin relaxation

“…The quadrupole Kondo effect and non-Fermi-liquid behavior in non-Kramers-doublet systems has also been discussed for (Pr,La)Pb 3 , 10 PrMg 3 , 11 PrInAg 2 , 12 PrV 2 Al 20 , 13 and PrNb 2 Al 20 . 14 Below 50 mK, superconductivity is observed in the resistivity and the ac magnetic susceptibility measurements. 3,4 This superconductivity is observed not in a part of the specimen, but in the entire volume of the specimen.…”