Determination of the crystal field parameters in SmFe11Ti

The magnetization of $\mathrm{Sm}{\mathrm{Fe}}₁₁\mathrm{Ti}$ single crystals has been measured along the principal crystallographic directions in steady (14 T) and pulsed (43 T) magnetic fields. The fourfold symmetry axis [001] is an easy magnetization direction. The magnetization curves measured in directions perpendicular to [001] are remarkable in two ways: (i) They do not depend on orientation of $\mathbit{H}$ within the basal plane; (ii) at low temperature they are $\mathsf{S}$ shaped, with an inflection point at about 0.6 times saturation magnetization. These two facts enable us to conclude that three out of five crystal field parameters of $\mathrm{Sm}{\mathrm{Fe}}₁₁\mathrm{Ti}$ are negligibly small; only ${A}₂⁰$ and ${A}₆⁰$ are essentially nonzero. A comparison with an isomorphous compound ${\mathrm{DyFe}}₁₁\mathrm{Ti}$ reveals a dramatic disparity of their crystal fields, especially as regards ${A}₄⁴$, nearly zero in $\mathrm{Sm}{\mathrm{Fe}}₁₁\mathrm{Ti}$ but outstandingly large in ${\mathrm{DyFe}}₁₁\mathrm{Ti}$.