Slow spin tunneling in the paramagnetic phase of the pyrochlore Nd2Sn2O7

Abstract

The insulating pyrochlore compound Nd2Sn2O7 has been shown to undergo a second order magnetic phase transition at Tc ≈ 0.91 K to a noncoplanar all-in-all-out magnetic structure of the Nd 3+ magnetic moments. An anomalously slow paramagnetic spin dynamics has been evidenced from neutron backscattering and muon spin relaxation (µSR). In the case of µSR this has been revealed through the strong effect of a 50 mT longitudinal field on the spin-lattice relaxation rate. Here, motivated by a recent successful work performed for Yb2Ti2O7 and Yb2Sn2O7, analyzing the shape of the µSR longitudinal polarization function, we substantiate the existence of extremely slow paramagnetic spin dynamics in the microsecond time range for Nd2Sn2O7. Between 1.7 and 7 K, this time scale is temperature independent. This suggests a double spin-flip tunneling relaxation mechanism to be at play, probably involving spin substructures such as tetrahedra. Unexpectedly, the standard deviation of the field distribution at the muon site increases as the system is cooled. This exotic spin dynamics is in sharp contrast with the dynamics above 100 K which is driven by the Orbach relaxation mechanism involving single Nd 3+ magnetic moments.

Intrinsic quantum Ising model on a triangular lattice magnet TmMgGaO4

“…For the DO doublet, the wave function of each state in the doublet is a linear superposition of |J z = 3n/2 where n is an odd integer. The DO doublet was found to be applicable to Nd 3+ in Nd-based pyrochlores [37][38][39][40][41][42][43][44], Sm 3+ in Sm 2 Ti 2 O 7 [45,46], Ce 3+ in Ce 2 Sn 2 O 7 [34,47,48], and Ce 2 Zr 2 O 7 [49][50][51] and Er 3+ in the spinels [52,53]. DO doublets can broadly exist in magnets with a D 3d point-group symmetry, other lattices such as honeycomb magnets could support the DO doublet [54].…”

Long-range dynamical magnetic order and spin tunneling in the cooperative paramagnetic states of the pyrochlore analogous spinel antiferromagnets CdYb2X4 ( X=S<

“…It has been recently shown that careful analyses of µSR spectra recorded in correlated paramagnetic regimes can yield useful information [31,42]. The spectra for the two compounds of interest here are best described as the weighted sum of two dynamical Kubo-Toyabe functions; see Fig.…”

Ground-state phase diagram of dipolar-octupolar pyrochlores

“…"Dipolar-octupolar" (DO) pyrochlores R 2 M 2 O 7 (R=Ce, Sm, Nd; M=Zr, Hf, Ti, Sn, Pb) [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44] constitute an opportunity in this context, with their low-energy physics being described by a simple XY Z Hamiltonian [45,46]. Out of this family, Ce 2 Sn 2 O 7 [27,28] and Ce 2 Zr 2 O 7 [29,30] have been highlighted recently as showing evidence of QSL physics.…”