Dynamic Spin Ice:Pr2Sn2O7

Abstract

In this Letter, we report a new spin ice--Pr2Sn2O7--which appears to have enhanced residual entropy due to the dynamic nature of the spins. Neutron scattering experiments show that at 200 mK, there is a significant amount of magnetic diffuse scattering which can be fit to the dipolar spin-ice model. However, these short-ranged ordered spins have a quasielastic response that is atypical of the canonical spin ices, and suggests that the ground state is dynamic (i.e., composed of locally ordered two-in-two-out spin configurations that can tunnel between energetically equivalent orientations). We report this as an example of a dynamic spin ice down to 200 mK.

Structural and magnetic properties of two branches of the tripod-kagome-lattice familyA2R3Sb3O14(ADun1, Trinh2, Lee3 et al. 2017Phys. Rev. BSelf Cite4513583View full textAdd to dashboardCite

“…For ZnPr (Fig. 6(b)), LRO (6) Interlayer RE-RE 6.23482(6) 6.22936(6) 6.16099(5) 6.14852(9) 6.14016 (7) 6.13020(6) 6.11863 (7) is also not observed in χ ac where a Curie-Weiss type behavior is persistent down to the lowest measured temperature of 0.3 K. For both MgPr and ZnPr, the absolute values of C mag /T below 10 K is extremely small (< 0.1 J/K 2 per mol-Pr), in sharp contrast to that observed in Pr-pyrochlores within the same temperature range (∼ 2 J/K 2 per mol-Pr) 30,31 . The integrated magnetic entropy (S mag ) from 0.35 K to 6 K recovers ∼ 0.2 J/K per mol-Pr, a value that is 3% of Rln2.…”

“…In the Pr-pyrochlore compound, the single-ion ground state is a non-Kramers doublet with a large Ising-like anisotropy, whose first excited crystal electric field (CEF) level is a non-magnetic singlet that is well separated from the ground state doublet (18 meV 30,31 , where spin fluctuations from a quantum superposition of the spin ice manifold suppresses LRO.…”

“…Besides the four examples mentioned above, other members of the MgRE family, such as RE = Pr, Tb, Ho, Yb, could prove interesting. In the parent pyrochlore compounds with these four RE elements, different ground states have been reported, including a QSL 28 , a dipolar spin ice 29 , exchange spin ices 30,31 and a quantum spin ice 32,33 . What states will occur when confined to two-dimensions with one of the frustrating spins removed?…”

Magnetic and Thermal Properties of the Single Crystalline Pr2Zr2O7 in a [111] Field

“…A new class of spin ice has been recently proposed for Pr and Yb pyrochlores [7][8][9][10][11], in which quantum-mechanical exchange interactions predominately provides the ferromagnetic coupling between neighboring spins; hence, they are called "exchange(-based) spin ice". The classical dipolar interactions are one order of magnitude smaller than exchange interactions due to the small size of the magnetic moment (∼ 3µ B ).…”

Neutron scattering studies of spin ices and spin liquids

“…The dipolar interaction strength in Pr 2 Sn 2 O 7 is estimated at 0.13 K [138], and the crystal field scheme suggests that the moments are Ising-like, pointing in or out of the tetrahedra, again due to a doublet groundstate. Susceptibility [139], powder diffraction and spectroscopy measurements show diffuse scattering with a spin ice-like form, but accompanied by significant dynamics which are absent in classical spin ices [138]. There is an important difference between Pr 3+ , which is a nonKramers ion, and Yb 3+ which is a Kramers ion.…”