Crystal field excitations from $\mathrm{Y}{\mathrm{b}}^{3+}$ ions at defective sites in highly stuffed $\mathrm{Y}{\mathrm{b}}_2\mathrm{T}{\mathrm{i}}_2{\mathrm{O}}_7$

Abstract

The pyrochlore magnet $\mathrm{Y}{\mathrm{b}}_2\mathrm{T}{\mathrm{i}}_2{\mathrm{O}}_7$ has been proposed as a quantum spin ice candidate, a spin liquid state expected to display emergent quantum electrodynamics with gauge photons among its elementary excitations. However, $\mathrm{Y}{\mathrm{b}}_2\mathrm{T}{\mathrm{i}}_2{\mathrm{O}}_7$'s ground state is known to be very sensitive to its precise stoichiometry. Powder samples, produced by solid state synthesis at relatively low temperatures, tend to be stoichiometric, while single crystals grown from the melt tend to display weak "stuffing" wherein $\sim 2\%$ of the $\mathrm{Y}{\mathrm{b}}^{3+}$, normally at the $A$ site of the $A_2{B}_2{O}_7$ pyrochlore structure, reside as well at the $B$ site. In such samples $\mathrm{Y}{\mathrm{b}}^{3+}$ ions should exist in defective environments at low levels, and be subjected to crystalline electric fields (CEFs) very different from those at the stoichiometric $A$ sites. New neutron scattering measurements of $\mathrm{Y}{\mathrm{b}}^{3+}$ in four compositions of $\mathrm{Y}{\mathrm{b}}_{2+\mathrm{x}}\mathrm{T}{\mathrm{i}}_{2-\mathrm{x}}{\mathrm{O}}_{7-\mathrm{y}}$, show the spectroscopic signatures for these defective $\mathrm{Y}{\mathrm{b}}^{3+}$ ions and explicitly demonstrate that the spin anisotropy of the $\mathrm{Y}{\mathrm{b}}^{3+}$ moment changes from XY-like for stoichiometric $\mathrm{Y}{\mathrm{b}}^{3+}$, to Ising-like for "stuffed" $B$ site $\mathrm{Y}{\mathrm{b}}^{3+}$, or for $A$ site $\mathrm{Y}{\mathrm{b}}^{3+}$ in the presence of an oxygen vacancy.

12 pages, 8 figures, 3 tables. Article content is the same as the original version. Only a single word was corrected in the abstract and the abstract and title were re-written with MathJax

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Cited by in corpus (5)

• Quantum Spin Ice Dynamics in the Dipole-Octupole Pyrochlore Magnet Ce${}_2$Zr${}_2$O${}_7$
• Dilute stuffing in the pyrochlore iridate $E{u}_{2}I{r}_2{O}_7$
• Orientation Dependence of the Magnetic Phase Diagram of Yb${}_2$Ti${}_2$O${}_7$
• Effects of "stuffing" on the atomic and electronic structure of the pyrochlore Yb${}_2$Ti${}_2$O${}_7$
• The Spectral and Magnetic Properties of Er${}^{3+}$ and Yb${}^{3+}$ Ions in Y${}_2$Ti${}_2$O${}_7$ Crystals with a Pyrochlore Structure