Multiple Magnetic Transitions in the Trilayer Nickelate Pr${}_4$Ni${}_3$O${}_{10}$ Revealed by Muon-Spin Rotation

Abstract

A muon-spin rotation/relaxation ($\mu$SR) study of the trilayer Ruddlesden--Popper nickelate Pr${}_4$Ni${}_3$O${}_{10}$ was performed at ambient pressure and under hydrostatic pressure up to 2.2 GPa. Three magnetic transitions were identified at ambient pressure: the onset of spin-density-wave (SDW) order at $T_{\mathrm{SDW}}\simeq 158$ K, an intermediate-temperature transition at $T^{\ast }\simeq 90$--100 K, and a low-temperature transition at $T_{\mathrm{SDW}}^{\mathrm{Pr}}\simeq 25$--27 K. While the intermediate transition at $T^{\ast }$ induces only minor changes in the internal-field distribution, the transition at $T_{\mathrm{SDW}}^{\mathrm{Pr}}$ is accompanied by a pronounced reconstruction of the magnetic structure, consistent with previous reports attributing enhanced interlayer coherence to the ordering of the Pr sublattice. The high-temperature transition at $T_{\mathrm{SDW}}$ is characterized by the sharp development of static internal magnetic fields with a narrow transition width of $0.65(4)$ K. Weak-transverse-field measurements reveal a finite thermal hysteresis of $0.27(6)$ K, with $T_{\mathrm{SDW}}^{\mathrm{warming}}>T_{\mathrm{SDW}}^{\mathrm{cooling}}$, indicating weakly first-order-like behavior. Hydrostatic pressure suppresses $T_{\mathrm{SDW}}$ linearly and reduces the ordered Ni magnetic moment $M$, with corresponding rates of $\mathrm{d}{T}_{\mathrm{SDW}}/\mathrm{d}p=-4.9(1)$ K/GPa and $\mathrm{d}\ln M/\mathrm{d}p=-2.0(5)\times 10^{-2}$ GPa${}^{-1}$, respectively, thereby demonstrating a gradual weakening of the spin-density-wave instability under compression.

14 pages, 7 figures