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

Abstract

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-4f moment. Here, we show that the Ce-4f shell in Ce–Fe intermetallics is partially Kondo screened. The Kondo scale is dramatically enhanced by nitrogen interstitials suppressing the Ce-4f 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-4f single-ion anisotropy and show that even unscreened Ce-4f 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.

Effect of transition metal doping on magnetic hardness of CeFe$_{12}$-based compounds

“…The cell with space group P mmn has the lowest energy among the considered structures, so we choose it as the basic unit cell for the calculation of CeFe 11 X compounds presented later in this paper. We identify the use of structures with space group Imm2 in the earlier works [12,13,19,31] as one of the factors which may lead to the differences between our and previous results. The range of MAE obtained for structures with different space groups is from 1.00 to 1.15 MJ m −3 and the corresponding range for total magnetic moment (m) is from 21.24 to 22.50 µ B f.u.…”

“…In the heavy fermion regime, the local magnetic moment of Ce is shielded by conduction electrons that couple to a single Ce 4f electron to form a nonmagnetic single state [31]. This kind of heavy-fermionic behavior of Ce has been observed in families "1-5" (CeCo 5 ) [36] and "2-14-1" (Ce 2 Fe 14 B) [37] of hard-magnetic inter-TABLE VII: The magnetocrystalline anisotropy energy [MAE (MJ m −3 )], total magnetic moment [m], magnetic hardness [κ], orbital magnetic moment [m l (X)], and spin magnetic moment [m s (X)] calculated for various 3d, 4d, and 5d transition metal elements X in compounds CeFe 11 X (s.g. Pmmn, No.…”

High-Throughput Selection and Experimental Realization of Two New Ce-Based Nitride Perovskites: CeMoN3 and CeWN3

“…While most rare earth elements often display ferromagnetic (FM) correlations, Ce 3+ cations are affected by two competing interactions: indirect exchange mediated by conduction electrons (i.e., the RKKY interaction), 58 , 59 which generally stabilizes the AFM order, 60 − 63 and Kondo screening, which leads to a nonmagnetic ground state. 64 , 65 Only occasionally is a FM ground state observed, either via an itinerant mechanism or arising at very low temperatures in fierce competition with AFM order. 66 , 67 However, the possibility of Ce in a mixed +3/+4 valence state, which typically carries no stable magnetic moment, must also be considered; this is reported to be the ground state of CeN.…”

“…Both simple pictures f 1 Ce 3+ or d 1 W 5+ /Mo 5+ are possible because AFM correlations are common in both. While most rare earth elements often display ferromagnetic (FM) correlations, Ce 3+ cations are affected by two competing interactions: indirect exchange mediated by conduction electrons (i.e., the RKKY interaction), , which generally stabilizes the AFM order, − and Kondo screening, which leads to a nonmagnetic ground state. , Only occasionally is a FM ground state observed, either via an itinerant mechanism or arising at very low temperatures in fierce competition with AFM order. , However, the possibility of Ce in a mixed +3/+4 valence state, which typically carries no stable magnetic moment, must also be considered; this is reported to be the ground state of CeN . Future work incorporating other magnetic transition metals (TMs)such as 3 d TMs (e.g., Fe, Co, Mn, ...) or 4 d /5 d TMs (e.g., Re, Ir, Ru, ...) that often cause useful or exotic magnetism in oxide perovskiteswould be intriguing but may be difficult given charge balance requirements for nitride perovskites.…”

Structure and Magnetic Properties of Intermetallic Rare-Earth-Transition-Metal Compounds: A Review

“…The microstructure must allow reaching the highest possible coercivity and remanent induction and a magnetization loop close to a rectangular one. The achievement of each of these objectives is facilitated by the existence of a granular microstructure [ 2 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 ].…”