Jahn-Teller stress effects on the magnetization and ESR properties of LaSb: Dy single crystals

We demonstrate that the ion-lattice interaction plays a significant role in the magnetization and ESR properties of LaSb: Dy single crystals. We provide a free-energy calculation to demonstrate that the applied magnetic field distorts locally the crystal around the Dy ion leading to a deviation of the Dy magnetic moment with respect to that expected from "pure" crystal-field effects. The fitting of the experimental magnetization data, measured along the [001] direction, to the theory based on our free-energy calculation, enables us to extract the coupling constant between the ${\Gamma }_3$ strain modes and the Dy ion to be $\left|V\right({\Gamma }_3\left)\right|=24\mathrm{}$ K. Analysis of the angular dependence of the ESR line shape strongly supports the hypothesis that only ${\Gamma }_3$ strains play a role in the ESR experiment. The combined ESR and magnetization data yield the width of the ${\Gamma }_3$ strain distribution to be ${\sigma }_3=1.25\mathrm{}\times {10}^{-3\mathrm{}}$. Using the value $V\left({\Gamma }_3\right)=24\mathrm{}$ K, our free-energy calculation clearly shows softening of the elastic constants of force at low temperatures. This can provide a mechanism for the large strain effects in our ESR. It indicates "single-ion" Jahn-Teller effects in LaSb: Dy at low temperatures.