Results of x-ray powder diffraction and magnetic measurements performed on $R{\mathrm{Fe}}_{11.3}{\mathrm{W}}_{0.7}$ compounds, where $R=\mathrm{Dy},$ Ho, Er, and Lu, are presented. The Curie temperature, saturation magnetization, and spin reorientation transitions are discussed in relation to several $R{\mathrm{Fe}}_{12-x}{T}_x$ systems, where $T=\mathrm{Ta},$ Nb, Mo, Ti, and the x-substituent concentration is within a narrow range $x=0.5\mathrm{}–\mathrm{1.0.}$ In these systems, the dependence of the Curie temperature versus the unit cell volume, for a given R partner, suggests combined size and electronic effects produced by the T atom. The strengths of the rare-earth–iron and iron-iron exchange interactions are evaluated in the mean-field framework, and analyzed with reference to $R{\mathrm{Fe}}_{12-x}{T}_x$ compounds, with $T=\mathrm{Ta},$ Re, Nb, Mo, Ti, Cr, and V. Based on (i) the phenomenological mean-field model accounting for the sublattice of conduction band electrons, (ii) Brooks’ reinterpretation of Campbell’s formulation of the intersublattice exchange, and (iii) Wigner-Seitz cell analysis, we explore the role played by the conduction band electrons, particularly the nd-type electrons $(n=3,$ 4, 5), on the intersublattice exchange coupling in the iron-rich $R{\mathrm{Fe}}_{12-x}{T}_x$ class of compounds. It is proposed that the variation in the conduction-electron density, by varying the T element type and concentration, leads to a modification of the $5d$ band occupancy number and consequently, of the R-Fe intersublattice exchange coupling.

Co-Pd multilayers obtained by Pd capping of pre-deposited Co nanoparticles on amorphous alumina are systematically studied by means of high-resolution transmission electron microscopy, x-ray diffraction, extended x-ray absorption fine structure, SQUID-based magnetometry, and x-ray magnetic circular dichroism. The films are formed by CoPd alloyed nanoparticles self-organized across the layers, with the interspace between the nanoparticles filled by the non-alloyed Pd metal. The nanoparticles show atomic arrangements compatible with short-range chemical order of $\mathrm{L}{1}_0$ strucure type. The collective magnetic behavior is that of ferromagnetically coupled particles with perpendicular magnetic anisotropy, irrespective of the amount of deposited Pd. For increasing temperature three magnetic phases are identified: hard ferromagnetic with strong coercive field, soft-ferromagnetic as in an amorphous asperomagnet, and superparamagnetic. Increasing the amount of Pd in the system leads to both magnetic hardness increment and higher transition temperatures. Magnetic total moments of 1.77(4) ${\mu }_B$ and 0.45(4) ${\mu }_B$ are found at Co and Pd sites, respectively, where the orbital moment of Co, 0.40(2) ${\mu }_B$, is high, while that of Pd is negligible. The effective magnetic anisotropy is the largest in the capping metal series (Pd, Pt, W, Cu, Ag, Au), which is attributed to the interparticle interaction between de nanoparticles, in addition to the intraparticle anisotropy arising from hybridization between the $3d–4d$ bands associated to the Co and Pd chemical arrangement in a $\mathrm{L}{1}_0$ structure type.

Mn ²⁺ substitution creates a compositional gradient that induces core–shell magnetic behavior, enabling precise anisotropy tuning for magnetic hyperthermia.

Supramolecular magnetic chains of Fe₃ cluster in a molecular complex.