Pressure-Induced Super Heavy Fermion State and Antiferromagnetism in YbIr₂Zn₂₀

Abstract

We studied an effect of pressure on the electronic state of YbIr 2 Zn 20 under magnetic fields. The heavy fermion state at ambient pressure is found to be changed into an antiferromagnetic state at pressures larger than a critical pressure P c 5.2 GPa, where the electronic state indicates a superheavy fermion state with an order of the electronic specific specific heat coefficient γ = 20 J/(K 2 ·mol). The temperature dependence of the electrical resistivity shows a characteristic two-peak structure above 5.0 GPa, implying the combined phenomena between the Kondo effect and the crystalline electric field effect. At 7.6 GPa, the magnetoresistance shows a broad maximum at a critical field H c , corresponding to a pressure-induced antiferromagnetic phase with the Néel temperature T N = 1.4 K. T N increases with further increasing pressure.

Collapse of the Kondo state and ferromagnetic quantum phase transition in YbFe2Zn20

“…At p c , a possibly ferromagnetic transition T M suddenly appears at ∼ 1 K and stays unchanged with further increasing pressure. This suggests that for YbFe 2 Zn 20 , the quantum criticality is avoided by going through a first-order QPT under pressure, which is in contrast to the YbCo 2 Zn 20 and YbIr 2 Zn 20 , where they enter AFM ordered states through QCP [26,39,44]. At high temperature, a continuously increase of the resistivity with pressure was observed for p p c (Fig.…”

“…Taking GdT 2 Zn 20 series for example, ferromagnetic ordered ground state is found for members in the iron column (T = Fe, Ru and Os) while antiferromagnetic ordered ground state in the cobalt column (T = Co, Rh and Ir) [31]. Moreover, the pressure-induced ordered states in YbCo 2 Zn 20 and YbIr 2 Zn 20 have also been suggested as AFM ordering [39,44]. Taking YbFe 2 Zn 20 in this study together, RT 2 Zn 20 family seems to follow the rule that for the iron column members, ferromagnetic ordering is expected, while for the cobalt column members, antiferromagnetic ordering is expected.…”

“…Apart from this, a field induced ordered phase has been observed at the ambient pressure in YbCo 2 Zn 20 , possibly due to the crystal electric field level crossing [36][37][38][39][40][41]. A pressure induced QCP has also been estimated for YbIr 2 Zn 20 (≈ 5.2 GPa) and YbRh 2 Zn 20 (≈ 5.2 GPa), however, for YbRh 2 Zn 20 no pressure induced magnetic transitions have been observed so far [42][43][44][45].…”