Intrinsically weak magnetic anisotropy of cerium in potential hard-magnetic intermetallics

Anna Galler (1) , Semih Ener (2) , Fernando Maccari (2) , Imants Dirba (2) , Konstantin P Skokov (2) , Oliver Gutfleisch (2) , Silke Biermann (1) , Leonid V Pourovskii (1)

1 CPHT - Centre de Physique Théorique [Palaiseau]
2 Darmstadt University of Technology [Darmstadt]

Cerium-based intermetallics are currently attracting much interest as a possible alternative to existing high-performance magnets containing scarce heavy rare-earth elements. However, the intrinsic magnetic properties of Ce in these systems are poorly understood due to the difficulty of a quantitative description of the Kondo effect, a many-body phenomenon where conduction electrons screen out the Ce-4 f moment. Here, we show that the Ce-4 f shell in Ce–Fe intermetallics is partially Kondo screened. The Kondo scale is dramatically enhanced by nitrogen interstitials suppressing the Ce-4 f contribution to the magnetic anisotropy, in striking contrast to the effect of nitrogenation in isostructural intermetallics containing other rare-earth elements. We determine the full temperature dependence of the Ce-4 f single-ion anisotropy and show that even unscreened Ce-4 f moments contribute little to the room-temperature intrinsic magnetic hardness. Our study thus establishes fundamental constraints on the potential of cerium-based permanent magnet intermetallics.

Domaines: Electrons fortement corrélés [cond-mat.str-el]; Science des matériaux [cond-mat.mtrl-sci]

Anna Galler, Semih Ener, Fernando Maccari, Imants Dirba, Konstantin P Skokov, et al.. Intrinsically weak magnetic anisotropy of cerium in potential hard-magnetic intermetallics. Npj Quantum Materials, 2021, 6 (1), ⟨10.1038/s41535-020-00301-6⟩. ⟨hal-03203602⟩