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Nanostructured transition metal dichalcogenide MnSe2 has attracted much attention due to its fascinating magnetic properties. In this article, a series of MnSe2 nanoparticles with different particle sizes are successfully prepared by a facile top‐down method of solid‐state reaction combined with ball milling, and the effects of ball milling on the phase composition, microstructure and magnetic properties of the MnSe2 are systematically studied. The results show that pure MnSe2 microparticles are obtained by the solid‐state reaction, however, partial MnSe2 is decomposed after ball milling for 16 h. The average particle size of the MnSe2 gradually decreases with the increase of milling time. MnSe2 nanoparticles with average particle size approximately 65 nm are obtained after milling for 40 h. After milling, the antiferromagnetic MnSe2 nanoparticles exhibit weak ferromagnetic characteristics due to the surface effect and the microstrain induced by ball milling. The residual magnetization (Mr) and coercivity (Hc) of the sample gradually increase as the particle size decreases. The Mr and Hc of the sample milled for 40 h reach 70.13 × 10−4 emu g−1 and 67.47 Oe, respectively. [ABSTRACT FROM AUTHOR]

NaZn 13 -type La(Fe,Si) 13 alloys are one of the most promising magnetocaloric materials near room temperature. However, the impact of lanthanide doping on their magnetocaloric properties has not been thoroughly investigated. Here, a series of Gd-doped La 1− x Gd x Fe 11.5 Si 1.5 (x = 0, 0.05, 0.1, 0.15, 0.2, 0.25) alloys were designed and synthesized by arc melting and annealing. The microstructure of different phases and their influence on magnetic properties were investigated. The Gd doping at La sites was confirmed by the lattice contraction revealed by X-ray diffraction and elemental mapping analysis. After saturation at around x = 0.1, extra Gd leads to formation of Gd-rich Gd 2 Fe 16 Si phase. Moreover, doping of extra Gd inhibits the formation of La(Fe,Si) 13 phase, resulting in significantly increased amount of the impurity phases (α-Fe and LaFeSi phase). The change of microstructure and composition causes the magnetic transition to shift from first order to second order. Because of Gd doping, the Curie temperature of La 1− x Gd x Fe 11.5 Si 1.5 increases, and the maximum entropy change decreases. Understanding the effect of Gd on the microstructure and magnetic properties can help us develop more rare-earth-doped La(Fe, Si) 13 alloys. • The microstructure, phase composition and magnetic properties of Gd-doped La 1− x Gd x Fe 11.5 Si 1.5 alloy have been investigated. • Atomic resolution STEM imaging and EDS elemental analysis have been performed at the phase boundaries in the alloys. • The effect of Gd doping on the microstructure and magnetic properties of La 1− x Gd x Fe 11.5 Si 1.5 alloys was discussed. [ABSTRACT FROM AUTHOR]