Competing interactions and magnetic frustration in Yb4LiGe4

Abstract

We have studied polycrystalline Yb 4 LiGe 4 , a ternary variant of the R 5 T 4 family of layered compounds characterized by a very strong coupling between the magnetic and crystallographic degrees of freedom. The system is mixed valent, with non-magnetic Yb 2+ and magnetic Yb 3+ present, and is characterized by coexisting ferromagnetic and antiferromagnetic correlations. We present measurements of resistivity, AC-susceptibility, specific heat, and muon spin relaxation (μSR), below 1 K. The low temperature measurements suggest a transition to a mesoscopically inhomogeneous magnetically ordered state below 2 K characterized by fluctuations well below the ordering temperature. This unusual state is believed to result from the enhanced twodimensionality produced by Li substitution and frustration effects inherent in the Yb sub-lattice geometry.2

EuLiGe2 and YbLiGe2 – A Divalent and an Intermediate‐Valent Compound with CaLiSi2‐Type Structures

“…Several systems combining rare earth elements with germanium and lithium have been studied 9. Other than in our recent work on Yb 4 LiGe 4 , the physical properties of these compounds have not been studied in detail 9,10. The low heats of vaporization of europium and ytterbium11 limit the synthesis of their compounds compared to other phases based on rare earth metals.…”

“…[5,6] Eu 2 LiGe 3 crystallizes in an orthorhombic Ca 2 LiSi 3 -type structure, and its detailed crystal structure and electronic characterization were studied by Xie et al [6] They also observed EuLiGe 2 as a side product during their synthesis of Eu 2 LiGe 3 . [8][9][10] Several systems combining rare earth elements with germanium and lithium have been studied. The single-crystal structure of YbLiGe 2 was studied.…”

“…The single-crystal structure of YbLiGe 2 was studied. [9,10] The low heats of vaporization of europium and ytterbium [11] limit the synthesis of their compounds compared to other phases based on rare earth metals. [8][9][10] Several systems combining rare earth elements with germanium and lithium have been studied.…”

“…The single‐crystal structure of YbLiGe 2 was studied 7. It is also interesting to note that only the first half of the lanthanides (La–Eu) and Yb form RELiGe 2 and the other rare earths are stable as RE 4 LiGe 4 8–10. Several systems combining rare earth elements with germanium and lithium have been studied 9.…”

Low-temperature nuclear magnetic resonance investigation of systems frustrated by competing exchange interactions

“…There are three degenerate configurations for the ground state where we can arrange the spins so that two bonds are AFM and one bond is FM ( Fig. 2 as in Villain model [36], in R 5 T 4 (R = rare earth, T = Ge or Si) [37] where the FM intra-layer interaction competes with the AFM inter-layer interaction, in J 1 − J 2 square lattice where FM NN (along the side) and AFM next-nearest-neighbor (NNN) interactions are comparable (to be discussed later in this chapter), in double pervoskite (A 2 BB O 6 , A = Ca, Ba, Sr, B, B = transition metals) family of compounds [38] where inequivalent NN and NNN exchange interactions compete, in spinels AB 2 O 4 where frustration arises since within each sublattice there is AFM coupling (to be discussed later in this chapter), and in spin ladder compounds [39] where frustrated interchain exchange interactions occur both on rungs and diagonals. Since frustration results in multi-degenerate ground states rather than one unique stable one, introduction of very small perturbations or fluctuations in the system cause very novel and exotic phenomena to emerge many of which have not been well explained or understood yet.…”