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Memory shape magnetic alloys, especially Heusler alloys, are important materials in replacing conventional cooling with magnetic systems. In the present study off stoichiometric Heusler alloys with nominal composition Χ50Υ25+xΖ25‐x (X = Ni; Y = Mn; Z = Sn; x = 13, 14) were prepared by arc melting followed by thermal treatment. Structural properties were analyzed with X‐ray diffraction at room temperature (RT) and at elevated temperatures, above the martensite—austenite transition area, to determine the relevant crystallographic parameters and observe the transition. Martensite stabilization at RT appears to be a challenge, coexistence of martensite—austenite phases were observed and calculated for both 38–12 and 39–11 (16% and 12% austenite, respectively). Magnetization measurements versus temperature and field were recorded in the areas of interest where 1st order transitions were expected (355 K for x = 13 and 408 K for x = 14), and the magnetic entropy's changes (ΔSm) were determined [0.4 (J/kgK) for x = 13 and 0.3 J/(kgK) for x = 14; Hmax = 1 T]. The complex character of the magnetic properties and their dependence on Mn‐Sn ratio and on the distance between Mn atoms is discussed. The structure and the lattice parameters were determined using an anisotropic strain broadening model; stress and strain were detected in the structure due to crystal phase coexistence. [ABSTRACT FROM AUTHOR]

Ordered L10 and high coercivity FePt nanoparticles were successfully synthesized via a chemical method using pre-synthesized Au nanoparticles as nuclei seeds. The size of the Au nanoparticles seems to play a significant role in the formation of the tetragonal phase (L10) FePt colloidal nanoalloys. Seeding with ∼12 nm diameter monodispersed Au nanoparticles in the reaction mixture was found to lead to partial L10 FePt particles with 2.8 kOe coercivity at room temperature, while seeding with ∼6 nm Au nanoparticles leads to the formation of well L10 ordered FePt colloidal particles with 8.8 kOe coercivity at room temperature, one of the highest values for the direct liquid phase synthesis of L10 FePt colloidal particles. Furthermore, seeding with smaller Au particles decreases the ordering temperature from 360 °C to 300 °C leading to the formation of more uniform well-shaped nanoparticles. [ABSTRACT FROM AUTHOR]