[PC7] Nickelates

1:45 PM - 2:15 PM JST(4:45 AM - 5:15 AM UTC)

[PC7-02-INV] Spin density wave order with single spin-spinless-stripe in La₃Ni₂O₇ probed by ¹³⁹La-NQR

*Hidekazu Mukuda¹ (1. Osaka University (Japan))

Keywords:

Nickelate,NMR,NQR,Spin density wave,high pressure

Remarkable high-T_c superconductivity (SC) with T_c ~ 80K was reported for bilayered nickelate La₃Ni₂O₇ under high pressure. In the previous ¹³⁹La-NMR studies at ambient pressure, the emergence of density wave order was microscopically observed below T*~ 150 K for La₃Ni₂O_7-δ and ~130 K for trilayered La₄Ni₃O_10-δ through the measurements of the NMR spectra and the nuclear spin relaxation rate[1]. In order to reveal the spin and/or charge states in the density wave order phase, we have performed ¹³⁹La-nuclear quadrupole resonance (NQR) measurements on these compounds at ambient pressure[2]. There are two crystallographically-inequivalent La sites, the La(1) site between the NiO₂ planes and La(2) site at the out-of-plane blocking layers. The La(2)-NQR study in bilayered La₃Ni₂O₇ clearly distinguishes the La(2)a site of the ideal La₃Ni₂O₇ from the other La(2)b site close to the local defects. Below 150K, almost half of the intrinsic La(2)a sites are dominated by a finite internal field within the ab plane, while the other half is dominated by a zero internal field. The result is consistently explained by the spin-density wave (SDW) order with single spin-spinless-stripe, where the reduced Ni magnetic moments are parallel to the ab-plane. Even for the La(2)b site close to the defects, the result is explained within the same model by considering the inhomogeneous internal magnetic fields that are enhanced around the nearby defects. These results provide unambiguous microscopic evidence for the SDW order with single spin-spinless-stripe below 150 K in La₃Ni₂O₇ at ambient pressure[2]. Recently we also performed the NQR measurement on trilayered La₄Ni₃O₁₀ and detected the different type of the density wave order state at intrinsic La(2) sites [3]. These results will provide further insight into understanding the relationship with the high-T_c states at high pressure in these nickel oxides.