Interplay of Charge-Density Wave and Magnetic Order in Ternary Rare-Earth Nickel Carbides, RNiC₂ (R=Pr and Nd)

Abstract

The electrical and structural properties of NdNiC 2 and PrNiC 2 are examined in single-crystalline samples in order to investigate the interplay of charge-density wave (CDW) and magnetic order in ternary rare-earth nickel carbides, RNiC 2 , where R is a rare-earth element. PrNiC 2 (no magnetic order down to 1.5 K) and NdNiC 2 [antiferromagnetic (AF) transition at 17.2 K] show resistance anomalies at 89 and 121 K, respectively, which are revealed to be CDW transitions by observing X-ray satellite reflections. NdNiC 2 also shows a gradual decrease in both resistivity and CDW amplitude below the Néel temperature. In the AF phase, the magnetoresistance sharply decreases where a ferromagnetic (FM) order occurs, which is realized above the spin-flop magnetic field. These results clearly suggest that the relationships between CDW and magnetic order in RNiC 2 depend on whether the magnetic order is AF or FM.Charge-density wave (CDW) transition is one of the representative phenomena in low-dimensional materials, and is actively investigated in the field of high-T C superconductors. The nesting of low-dimensional Fermi surfaces leads to electronic instability, i.e., Peierls instability, which induces CDW, that is, a periodic charge density modulation coupled to an underlying lattice by the electron-lattice interaction. 1) Since the discovery of CDW transitions in real materials, such as the quasi-1D organic conductor, TTF-TCNQ, 2) and inorganic compounds, K 0:3 MoO 33) and NbSe 3 , 4) peculiar phenomena, such as the dynamics of CDW sliding and low-dimensional fluctuation above the transition temperature, have been intensively studied.The recent target of the study of CDW has changed from the physical property itself to understanding competing phenomena between a CDW and other electronic phases, such as superconductivity 5) and magnetism. In the latter topic, there have been few reports of a clear coupling between a CDW and a magnetic order, although some intermetallic rare-earth compounds in which a CDW and an antiferromagnetic (AF) order coexist, such as Er 5 Ir 4 Si 10 , have been reported. 6,7) Recently, a strong interplay of a CDW and a ferromagnetic (FM) order was reported in one of the ternary rareearth nickel carbides, SmNiC 2 . 8,9) This compound has a CDW transition at 148 K and the CDW is suppressed at 17.7 K, where an FM order occurs. SmNiC 2 belongs to the RNiC 2 (R: rare-earth element) family that crystallizes in the CeNiC 2 -type orthorhombic structure (space group: Amm2). 10) In this system, nickel atoms are not magnetic and rare-earth elements mainly contribute to the magnetic properties showing the character of interacting local magnetic moments through the RKKY interaction. 11) In the early 1990s, magnetic structures in RNiC 2 had been intensively investigated and various magnetic orders had been reported, such as an incommensurate-commensurate AF transition in DyNiC 2 , 12) an FM order in SmNiC 2 , and AF orders in CeNiC 2 and NdNiC 2 . 13) In the 2000s, Murase et al. reported that some RNiC 2 compounds ...

Magnetism and charge density waves inRNiC2(R=Ce,Pr,Nd)

“…Most of the members of the latter family exhibit the Peierls transitions towards the charge density wave state 27 . The relevance of a Peierls instability has been confirmed for R = Gd, Tb, Nd, Pr and Sm, while the LaNiC 2 and CeNiC 2 compounds do not show any anomalies that could be attributed to CDW [28][29][30][31][32] . Instead, LaNiC 2 is an unconventional noncentrosymmetric superconductor with T c = 2.7 K [33][34][35] .…”

Field-induced suppression of charge density wave in GdNiC2

“…To support this scenario, we have followed an analysis proposed by Yamamoto et al 21 and compared the ratio of resistivity in GdNiC 2 measured at 2 K (thus in presence of magnetic order), with and without magnetic field, respectively and at a temperature slightly above the AF transition, with corresponding values obtained for and NdNiC 2 . In GdNiC 2 , ρ0T,2K…”

“…Agreement between q and the magnetic propagation vector leads to a sort of resonance, which prevents the local magnetic moments from breaking the pairing interaction and, in this scenario CDW and AF orders coexist 21 . Deviation from this condition leads then to breaking of the singlet electron -hole pairs forming the CDW.…”

“…ρ0T,23K = 0.18 21 . These quantities parallel relevant ratios for NdNiC 2 : in the presence of AF, partially suppressing CDW: R0T,5K R0T,20K ≃ 0.4 and R9T,5K R0T,20K ≃ 0.16 at the same temperature, albeit in the presence of a magnetic field in which the CDW is completely suppressed.…”

“…In fact, the case of chromium still engages great interest of researchers [11][12][13] . Recently, much attention has been devoted to the two families of intermetallic materials: M 5 Ir 4 Si 10 , where M = (Er, Yb, Dy, Ho, Y and Tm) [14][15][16][17][18][19] and RNiC 2 , where R = (Sm, Tb, Nd and Gd) [20][21][22] , in which the emergence of CDW and magnetic ordering has been observed. The study of physical properties of these compounds opens a wide road to explore the interplay between both phenomena.…”