Asphericity of magnetization density and anisotropy in rare-earth pyrochlores via polarized neutron diffraction and iterative entropy maximization

Abstract

The procedure of magnetization density reconstruction in locally anisotropic magnetics with unquenched orbital moment is developed, based on the iterative entropy maximization and the site susceptibility approach. The procedure provides simultaneously model-free site susceptibility parameters of the $R$ ions and the shape of the magnetization distribution. The reconstruction of a noncollinear magnetic moment distribution was applied to rare-earth pyrochlore compounds ${R}_{2}{\mathrm{Ti}}_{2}{\mathrm{O}}_{7}$ $(R=\text{Tb}, \mathrm{Ho}, \mathrm{Er}, \mathrm{Yb})$, which revealed an oblate asphericity of the ${\mathrm{Tb}}^{3+}$ magnetization density and a prolate one for the ${\mathrm{Ho}}^{3+}$ and ${\mathrm{Yb}}^{3+}$ ions. The noncollinear magnetic moment distributions are compared with these predicted by the single-ion anisotropy model, shedding light on the anisotropy of lanthanides with an unquenched orbital moment.