Frustrated Ising Chains in SrHo2O4

Jiajia Wen (Johns Hopkins University)

The 1-dimentional J1-J2 Ising spin chain with nearest and next nearest neighbor interactions is one of the simplest models where competing interaction induces spatially modulated structures. In this model, a transition point at J2/J1=1/2 separates ground states that double and quadruple the unit cell respectively. While exact theoretical results for the T-dependent two point spin correlations are available, realization of such models in real material has not been discovered before.

I will report an unexpected realization of J1-J2 Ising chains in SrHo2O4. In this material the 3-dimensional magnetic lattice is partitioned into two sets of weakly coupled Ising chains with orthogonal spin orientations due to crystalline electric field effect. Through elastic neutron scattering, magnetization, and specific heat measurements, these two types of chains are shown to straddle the previously mentioned transition point. Below temperature of 0.7 K, the Neel chains forms 3-dimentional long range order, while the double-Neel chains lock into an incommensurate state with anisotropic correlation: long range order along the chain direction and short range, possibly critical correlations in the transverse directions. We argue the lack of conventional three dimensional long range order on the double-Neel chains in this clean system is due to kinetically trapped defects that disrupt inter-chain correlation.

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