Disorder from order among anisotropic next-nearest-neighbor Ising spin chains in SrHo$_2$O$_4$

We describe why Ising spin chains with competing interactions in $\rm SrHo_2O_4$ segregate into ordered and disordered ensembles at low temperatures ($T$). Using elastic neutron scattering, magnetization, and specific heat measurements, the two distinct spin chains are inferred to have Néel ($\uparrow\downarrow\uparrow\downarrow$) and double-Néel ($\uparrow\uparrow\downarrow\downarrow$) ground states respectively. Below $T_\mathrm{N}=0.68(2)$~K, the Néel chains develop three dimensional (3D) long range order (LRO), which arrests further thermal equilibration of the double-Néel chains so they remain in a disordered incommensurate state for $T$ below $T_\mathrm{S}= 0.52(2)$~K. $\rm SrHo_2O_4$ distills an important feature of incommensurate low dimensional magnetism: kinetically trapped topological defects in a quasi$-d-$dimensional spin system can preclude order in $d+1$ dimensions.

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