Homogeneous reduced moment in a gapful scalar chiral kagome antiferromagnet

We present a quantitative experimental investigation of the scalar chiral magnetic order with in Nd₃Sb₃Mg₂O₁₄. Static magnetization reveals a net ferromagnetic ground state, and inelastic neutron scattering from the hyperfine coupled nuclear spin reveals a local ordered moment of 1.76(6) ${\mathrm{micro}}_B$, just 61(2)% of the saturated moment size. The experiments exclude static disorder as the source of the reduced moment. A 38(1) $\mathrm{micro}\text{eV}$ gap in the magnetic excitation spectrum inferred from heat capacity rules out thermal fluctuations and suggests a multipolar explanation for the moment reduction. We compare Nd₃Sb₃Mg₂O₁₄ to Nd pyrochlores and show that Nd₂Zr₂O₇ is in a spin fragmented state using nuclear Schottky heat capacity.