Pressure-Induced Split of the Density Wave Transitions in La₃Ni₂O7-δ

The unveiling of superconductivity in La₃Ni₂O7-δ under pressure, following the suppression of a high-temperature density wave (DW) state, has attracted considerable attention. Notably, the nature of this competing DW order remains elusive, presenting a crucial question that demands further investigation. Here, we employ the muon-spin rotation/relaxation (μSR) technique combined with dipole-field numerical analysis to probe the magnetic response of La₃Ni₂O7-δ as a function of hydrostatic pressure. At ambient pressure, μSR experiments reveal commensurate static magnetic order below TN 151K. The comparison of the observed internal magnetic fields with dipole-field calculations reveals the magnetic structure's compatibility with a stripe-type arrangement of Ni moments (0.3-0.7μB$), characterized by alternating lines of magnetic moments and non-magnetic stripes. Experiments under pressure (up to $p2.3$~GPa) demonstrate an increase of the magnetic ordering temperature at a rate ${ d}TN/{ d}p 2.8$ K/GPa. This trend is opposite in sign and significantly smaller in magnitude compared to the changes observed in the DW order of unknown origin reported by Wang et al. [arXiv:2309.17378]. Our findings reveal that the ground state of the La₃Ni₂O7-δ system is characterized by the coexistence of two distinct orders -- the spin density wave and, most likely, charge density wave -- with a notable pressure-induced separation between them.