Determination of the crystal field parameters in SmFe11Ti

L. V. B. Diop, M. D. Kuz’min, Y. Skourski, K. P. Skokov, I. A. Radulov, O. Gutfleisch Physical Review B 102, 064423 (2020) DOI:10.1103/PhysRevB.102.064423 SmFe 11 Ti is an interesting material not only from an application point of view as a permanent-magnet material, but also from a fundamental perspective as a model system for studying magnetic anisotropy and crystal fields. However, the few reports on the crystal field parameters of SmFe 11 Ti are all based on fitting a single magnetization curve. Here, the magnetization of SmFe 11 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 H within the basal plane; (ii) at low temperature they are 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 SmFe 11 Ti are negligibly small; only A02 and A06 are essentially nonzero. A comparison with an isomorphous compound DyFe 11 Ti reveals a dramatic disparity of their crystal fields, especially as regardsA 4 4 , nearly zero in SmFe 11 Ti but outstandingly large in DyFe 11 Ti.