Single-Ion Magnetostriction in Gd₂O₃–CeO₂ Solid Solutions

Ceria (CeO₂) and its solid solutions with Gd₂O₃ are technologically important and environmentally friendly materials with numerous interesting properties and important applications. Nevertheless, the magnetic properties of ceria are even today not fully understood, and magnetoelastic coupling in pure or doped ceria remains essentially unexplored. This has been so, in part, due to the difficulty of measuring very small magnetostrictive strains in weakly paramagnetic materials. During the last decade, however, technical advances have enabled sensitive and accurate measurements of sample deformation in high magnetic fields. Here, forced magnetostriction (MS) in Gd₂O₃-CeO₂ solid solution ceramics (Ce_1−xGd_xO_2−x/2, 0 ≤ x ≤ 1) at room temperature is characterized. In a pulsed magnetic field μ₀H ≤ 60 Tesla, longitudinal MS strain is observed to depend on the square of the field amplitude and to increase linearly with Gd³⁺ concentration but is not sensitive to the lattice symmetry of the ceramics. The theory attributes the origin of the observed strain to the single-ion MS response of Gd³⁺ to the crystal field via mixing of ground and excited electronic states and covalent hybridization with oxygen ligands. Contributions of charge-compensating oxygen vacancies and/or Van Vleck paramagnetism to the observed magnetoelastic coupling are determined to be negligible.