Non-Fermi Liquid Behavior Close to a Quantum Critical Point in a Ferromagnetic State without Local Moments

Abstract

A quantum critical point (QCP) occurs upon chemical doping of the weak itinerant ferromagnet Sc3.1In. Remarkable for a system with no local moments, the QCP is accompanied by non-Fermi liquid (NFL) behavior, manifested in the logarithmic divergence of the specific heat both in the ferro-and the paramagnetic states. Sc3.1In displays critical scaling and NFL behavior in the ferromagnetic state, akin to what had been observed only in f -electron, local moment systems. With doping, critical scaling is observed close to the QCP, as the critical exponents δ, γ and β have weak composition dependence, with δ nearly twice, and β almost half of their respective mean-field values. The unusually large paramagnetic moment µP M ∼ 1.3µB/F.U. is nearly composition-independent. Evidence for strong spin fluctuations, accompanying the QCP at xc = 0.035±0.005, may be ascribed to the reduced dimensionality of Sc3.1In, associated with the nearly one-dimensional Sc-In chains.arXiv:1410.6850v1 [cond-mat.str-el]

Quantum Critical Point in the Itinerant Ferromagnet Ni1−xRhx

“…4). This logarithmic divergence was previously reported in Ni 0.62 Rh 0.38 [39] and has also been observed in other QCP systems [9][10][11]40]. For x > x crit , C el /T levels off at the lowest temperatures, consistent with non-Fermiliquid (NFL) to FL crossover.…”

“…FM QCPs are revealed via chemical substitution in Zr 1−x Nb x Zn 2 [8], SrCo 2 (Ge 1−x P x ) 2 [9], YbNi 4 (P 1−x As x ) 2 [10], and (Sc 1−x Lu x ) 3.1 In [11]. The disorder effect is minimal or negligible in these systems.…”

Pressure effects in the itinerant antiferromagnetic metal TiAu

“…12 This contrasting behavior between the evolution of T N with P and x in Ti 1−x Sc x Au is similar to what was observed for the IFM Sc 3 In, in which the FM ordering temperature T C , is initially enhanced with increasing P but is monotonically suppressed toward a QCP with increasing x in (Sc 1−x Lu x ) 3.1 In. 22 In the Ti 1−x Sc x Au system, band structure calculations reveal that the 3d-electron bands of the Ti 4+ ions contribute the most to the sharp peak ob-served in the DOS(ǫ F ) that leads to the magnetic ground state. 12 As x increases, and more Sc 3+ ions replace the Ti 4+ ions, the peak in the DOS(ǫ) shifts away from the ǫ F leading to a reduction in the magnetic ordering temperature T N .…”

Field-induced quantum critical point in the new itinerant antiferromagnet Ti$_3$Cu$_4$

“…A wealth of local and intermediate moment systems are known, where this interplay is the origin of emergent phenomena such as unconventional superconductivity [1][2][3][4], non-Fermi liquid (NFL) behavior [5][6][7][8][9], and quantum criticality [10][11][12][13][14]. By contrast, the itinerant moment limit (where no partially-filled core electronic shells are involved in magnetism) has been realized experimentally in a minute number of compounds, the decades-old ferromagnets ZrZn 2 [15] and Sc 3.1 In [16,17], and the recentlydiscovered antiferromagnet TiAu [18]. Furthermore, the instances of quantum critical behavior are limited in the purely itinerant or intermediate moment systems, compared to the more ubiquitous occurrences in heavy fermion systems, when the tuning parameter is pressure or doping.…”

“…When the tuning parameter is either pressure or chemi-cal substitution, QCPs have been reported in a vast array of compounds [6,7,24] including in the itinerant magnets ZrZn 2 [15,25], Sc 3.1 In [16,17], and TiAu [18,26]. Comparatively, the number of field induced-QCPs is quite small, limited to heavy fermions such as YbRh 2 Si 2 [19], YbAgGe [20], CePdAl [21], CeCoIn 5 [22], CeAuSb 2 [27], YbPtIn [23], and Bose-Einstein condensates (BECs) in quantum magnets [28].…”