Ferromagnetic quantum critical point in CePd2P2 with Pd → Ni substitution

Abstract

An investigation of the structural, thermodynamic, and electronic transport properties of the isoelectronic chemical substitution series Ce(Pd1−xNix)2P2 is reported, where a possible ferromagnetic quantum critical point is uncovered in the temperature -concentration (T − x) phase diagram. This behavior results from the simultaneous contraction of the unit cell volume, which tunes the relative strengths of the Kondo and RKKY interactions, and the introduction of disorder through alloying. Near the critical region at xcr ≈ 0.7, the rate of contraction of the unit cell volume strengthens, indicating that the cerium f -valence crosses over from trivalent to a non-integer value. Consistent with this picture, x-ray absorption spectroscopy measurements reveal that while CePd2P2 has a purely trivalent cerium f -state, CeNi2P2 has a small (< 10 %) tetravalent contribution. In a broad region around xcr, there is a breakdown of Fermi liquid temperature dependences, signaling the influence of quantum critical fluctuations and disorder effects. Measurements of clean CePd2P2 furthermore show that applied pressure has a similar initial effect to alloying on the ferromagnetic order. From these results, CePd2P2 emerges as a keystone system to test theories such as the Belitz-Kirkpatrick-Vojta model for ferromagnetic quantum criticality, where distinct behaviors are expected in the dirty and clean limits.

Quantum Critical Point in the Itinerant Ferromagnet Ni1−xRhx

“…Ni 1−x Rh x shows the first occurrence of a FM QCP with dilution of the d-electron magnetic sublattice. This is in contrast with chemical substitution on the non-magnetic sublattice in other FM QCP systems [9,10,[18][19][20][21]. In particular, due to its chemical simplicity, Ni 1−x Rh x is an ideal platform for furture studies and our work establishes a new approach to explore FM quantum criticality.…”

“…Theoretical work by Belitz, Kirkpatrick, and Vojta (BKV) has proposed a route towards a FM QCP by long-range effective spin interactions that occur in the presence of quenched disorder [6,16,17]. A handful of FM QCPs have been identified as candidates for this phenomenology, including UCo 1−x Fe x Ge [18], (Mn 1−x Fe x )Si [19], NiCoCr x [20], and Ce(Pd 1−x Ni x ) 2 P 2 [21], where disorder is inherently introduced by the chemical substitution. In most of these systems, the proposed existence of a QCP is based on either divergence of some thermodynamic parameters [18,20,21] or the second order nature of the transition [19].…”

“…A handful of FM QCPs have been identified as candidates for this phenomenology, including UCo 1−x Fe x Ge [18], (Mn 1−x Fe x )Si [19], NiCoCr x [20], and Ce(Pd 1−x Ni x ) 2 P 2 [21], where disorder is inherently introduced by the chemical substitution. In most of these systems, the proposed existence of a QCP is based on either divergence of some thermodynamic parameters [18,20,21] or the second order nature of the transition [19]. However, the unambiguous identification of a QCP requires that both these criteria be fulfilled.…”

CRYSTAL STRUCTURE OF THE PHOSPHIDES RPd2P2 (R = Gd, Tb, Dy, AND Er)

“…Фосфіди складу RPd 2 P 2 , де R = Eu-Dy, мають парамагнітні властивості. Також відомо, що для сполуки CePd 2 P 2 властивий Кондо-ефект [19], а за низьких температур наявні феромагнітні впорядкування [20][21][22][23][24][25].…”

Quantum critical point in the itinerant ferromagnet Ni$_{1-x}$Rh$_x$

“…Theoretical work by Belitz, Kirkpatrick, and Vojta (BKV) has proposed a route towards a FM QCP by long-range effective spin interactions that occur in the presence of quenched disorder [6,16,17]. A handful of FM QCPs have been identified as candidates for this phenomenology, including UCo 1−x Fe x Ge [18], (Mn 1−x Fe x )Si [19], NiCoCr x [20], and Ce(Pd 1−x Ni x ) 2 P 2 [21], where disorder is inherently introduced by the chemical substitution.…”