Field-tuned Fermi liquid in quantum critical YFe2Al10

Abstract

We present here measurements of the magnetization M, ac susceptibility χ ′ , electrical resistivity ρ, and specific heat C in single crystals of metallic YFe2Al10. The magnetic susceptibility follows a Curie-Weiss temperature dependence for 75 K≤T≤750 K, with a fluctuating Fe moment of 0.45 µB/Fe, and the ac susceptibility χ ′ diverges at lower temperatures χ ′ ∼T −1.28±0.04 when the ac field is in the basal plane. The field B and temperature T dependencies of the magnetization M are well described by the scaling expression MT −β =F(B/T β+γ ) for 1.8 K≤T≤30 K and for fields larger than 0.1 T. These results indicate that strong quasi-two dimensional critical fluctuations are present that can be suppressed by magnetic fields. The magnetic and electronic parts of the specific heat CM show a similar divergence for 0.4 K≤T≤12 K, where CM /T∼T −0.47±0.03 . The divergences in χ ′ and CM /T indicate that YFe2Al10 is located near a quantum critical point, and no magnetic order is observed above 0.09 K. We argue that our results are inconsistent with quantum impurity or disorder models, suggesting instead that YFe2Al10 is on the verge of bulk magnetic ordering, and that the critical fluctuations that are associated with this quantum critical point lead to the divergencies in CM /T and χ ′ .

Quenching of spin fluctuations in the 3d and 4f aluminides YFe2Al10and YbFe2Al10: a comparative27Al NMR and specific heat study

“…In contrast, the new 3d-system YFe 2 Al 10, is proposed being located directly at a quantum critical point (QCP) with strong ferromagnetic (FM) correlations [4,5]. Among weak itinerant 3d-magnets, the existence of a FM QCP is a matter of controversy and upon external tuning only, first-order phase transitions are found [6].…”

“…At low temperatures, the contribution of Yb to the susceptibility is small and nearly constant and the magnetism here is dominated by the itinerant Fe subsystem. It is remarkable that the low-temperature increase in both systems is nearly identical and that they both share the same logarithmic dependence with the same characteristic energy scale of T 0 ¼ 2.1 K. For YFe 2 Al 10 , a weak power law T Àn divergence with n % 0.5 was suggested in C/T [4,5]. According to Moriya's SCR theory for weak ferromagnets one expects that g(T) / ln (1/T) and R(T) / T À4/3 for the SLR rates [11].…”

Quantum critical fluctuations in layered YFe 2 Al 10

“…The traditional pictures fail badly in YFe 2 Al 10 , suggesting that the fluctuating moments and the conduction electrons may not be entirely separable. Indeed, the low temperature resistive upturn is reminiscent of the Kondo effect in normal metals, and the B = 0 ρ(T) can be satisfactorily fitted (22) by the Kondo expression (38). However, the resistivity for a fixed number of Kondo compensated moments in a conventional metallic host scales with T/B (39,40), and so a different explanation is needed for the T/B 0.59 scaling found in YFe 2 Al 10 ( Fig.…”

“…When B ac is parallel to the b axis, χ ac does not diverge, and its value at 1.8 K is almost 30 times smaller than when the field is in the ac plane, where there is no measurable anisotropy. This divergence in χ ac does not culminate in magnetic order, at least for temperatures above 0.1 K (22). Instead it indicates that the Significance Temperature-driven phase transitions, such as the melting of ice or the boiling of water, are a familiar part of daily life.…”

“…Although YFe 2 Al 10 is not ordered above 0.1 K (22), the correlations that drive this quasi-2D metal to the brink of ferromagnetic order are derived from the hybridization of Fe-based d-electrons with conduction electrons. Disorder effects are expected to be minimal in this system, as single crystal X-ray diffraction measurements find no evidence of departures from stoichiometry or site disorder (22,23).…”