Search for a spin-nematic phase in the quasi-one-dimensional frustrated magnetLiCuVO4

Abstract

We have performed NMR experiments on the quasi one-dimensional frustrated spin-1/2 system LiCuVO4 in magnetic fields H applied along the c-axis up to field values near the saturation field Hsat. For the field range Hc2 < H < Hc3 (µ0Hc2 ≈ 7.5 T and µ0Hc3 = [40.5 ± 0.2] T) the 51 V NMR spectra at T = 380 mK exhibit a characteristic double-horn pattern, as expected for a spinmodulated phase in which the magnetic moments of Cu 2+ ions are aligned parallel to the applied field H and their magnitudes change sinusoidally along the magnetic chains. For higher fields, the 51 V NMR spectral shape changes from the double-horn pattern into a single Lorentzian line. For this Lorentzian line, the internal field at the 51 V nuclei stays constant for µ0H > 41.4 T, indicating that the majority of magnetic moments in LiCuVO4 are already saturated in this field range. This result is inconsistent with the previously observed linear field dependence of the magnetization M (H) for Hc3 < H < Hsat with µ0Hsat = 45 T [L. E. Svistov et al., JETP Letters 93, 21 (2011)]. We argue that the discrepancy is due to non-magnetic defects in the samples. The results of the spin-lattice relaxation rate of 7 Li nuclei indicate an energy gap which grows with field twice as fast as the Zeeman energy of a single spin, therefore, suggesting that the two-magnon bound state is the lowest energy excitation. The energy gap tends to close at µ0H ≈ 41 T. Our results suggest that the theoretically predicted spin-nematic phase, if it exists in LiCuVO4, can be established only within the narrow field range 40.5 < µ0H < 41.4 T .

Orbital Arrangements and Magnetic Interactions in the Quasi-One-Dimensional Cuprates ACuMoO4(OH) (A = Na, K)

“…In fact, the exchange interactions of NaCuMoO4(OH) are estimated as J1 = -51 K and J2 = 36 K. 14 Note that the two interactions cause frustration in the spin chain, because J1 favors all the spins in the same direction whereas J2 tends to make every second spins antiparallel. This frustration can lead to a variety of magnetic phases such as spin nematic order, which is theoretically predicted to be a sort of spin liquid with an unusual spin order analogous to the nematic state in liquid crystals [16][17][18][19] but has not yet been observed in actual compounds 20 .…”

Dynamics of linarite: Observations of magnetic excitations

“…The combination of low dimensionsality, frustration and quantum physics effectively suppresses conventional long range order down to very low temperatures, which can lead to unconventional magnetic states such as quantum spin liquids 1,2 , spin-Peierls states 3 and Tomonaga-Luttinger liquid phases 4 . Additionally, when a magnetic field is applied to such systems, a range of exotic states such as spin-multipolar phases [5][6][7][8][9] may be induced.…”

“…Especially, the so-called spin-nematic state has recently received strong interest [9][10][11][12][13][14] . The spin-nematic phase can be likened to the arrangement of molecules in nematic liquid crystals.…”

NaCuMoO4(OH) as a Candidate Frustrated J1–J2 Chain Quantum Magnet

“…Only NMR experiments were performed around the saturation, which revealed that the majority of magnetic moments were already saturated above 41.4 T, where the spin nematic phase was suggested from magnetization measurements. This discrepancy is likely due to crystal defects such as Li deficiency [31]. The other candidate compounds thus far studied also have some problems, such as disorder effects and the lack of large single crystals.…”

“…One more important requirement for a good candidate compound is the availability of a large and clean single crystal. Among the compounds shown in Table I [20][21][22], and LiCuVO 4 [23][24][25][26][27][28][29][30][31]. However, "a cleanness" of these crystals seems unsatisfactory: a natural crystal of PbCuSO 4 (OH) 2 is contaminated by impurities, and the two Li-containing crystals seem to suffer from Li deficiency or an interchange between Li and Cu atoms [24].…”