Field-temperature phase diagram and entropy landscape ofCeAuSb2

Abstract

We report a field-temperature phase diagram and an entropy map for the heavy-fermion compound CeAuSb 2 . CeAuSb 2 orders antiferromagnetically below T N = 6.6 K and has two metamagnetic transitions, at 2.8 and 5.6 T. The locations of the critical end points of the metamagnetic transitions, which may play a strong role in the putative quantum criticality of CeAuSb 2 and related compounds, are identified. The entropy map reveals an apparent entropy balance with Fermi-liquid behavior, implying that above the Néel transition the Ce moments are incorporated into the Fermi liquid. High-field data showing that the magnetic behavior is remarkably anisotropic are also reported.

Effect of applied orthorhombic lattice distortion on the antiferromagnetic phase of CeAuSb2

“…Therefore at T N the cerium moments should be incorporated into the Fermi sea, and there is thermodynamic evidence that they are: The heat capacity has a Fermi liquid form (i.e. proportional to T ) between T N and ∼10 K, and below T N shows good entropy balance with a Fermi liquid [10]. Recent neutron scattering data suggest that the magnetic order itself is itinerant [11]: It was found to be an incommensurate spin density wave polarised along the c axis, meaning that the polarisation must vary from site to site, which is not expected for local-moment order.…”

Microscopic Nature of Magnetic Ground State in CeAuSb2

“…It suggests that magnetic field application along [−HH0] direction, perpendicular to the scattering plane of the single crystal, does not induce any critical phase or, new phase transition in the system. Perhaps, even larger field than H = 9 T may be needed along the [−HH0] direction to induce the spin‐flop‐type transition to a metamagnetic phase in CeAuSb 2 , as reported previously for the field application along easy (001) direction …”

“…Previous reports have suggested that field application along the c ‐axis tends to induce a quantum critical phase in this compound . More recent works on the effect of magnetic field application along the easy [001] direction have revealed the field‐induced metamagnetic transition in this system . Future research works are highly desirable to understand the interplay between the low temperature quantum critical state and the metamagnetic phases in CeAuSb 2 .…”

“…Among Ce‐based heavy electron systems, stoichiometric CeAuSb 2 has emerged as the archetypal material to understand the origin of quantum critical phenomenon . Electrical resistivity measurements on the single‐crystal specimen of CeAuSb 2 have revealed an anomalous power–law exponent of resistivity, ∝ ρ ε with ε ≈ 0.5, characterizing it as a non‐Fermi liquid metal at low temperature .…”

“…The knowledge of ground‐state magnetic configuration is not only crucial to this debate, but also to understand the nature of possible quantum critical state in this system. In addition, CeAuSb 2 is argued to undergo through metamagnetic phase transition in magnetic field application along the [001] easy axis . Furthermore, application of an uniaxial pressure or strain tends to split the single antiferromagnetic transition into two metamagnetic phases .…”