Search

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 for room-temperature magnetic refrigeration. However, the narrow ferromagnetic-to-paramagnetic transition temperature range of La(Fe,Si) 13 alloys severely limited their magnetic refrigeration application. Herein, a series of La 1.4 Fe 11.8- x Co x Si 1.2 (x = 0.88, 0.94, 0.98, 1.02, 1.06) alloys were designed and prepared by high-energy ball milling and annealing. It is discovered that all the samples are composed of La(Fe,Co,Si) 13 main phase and a small amount of α -Fe phase. The Curie temperature of the ferromagnetic-to-paramagnetic transition was well adjusted to room temperature by optimizing the x. A maximum magnetic entropy change (- ΔS M) of 4.0 J kg−1 K−1 for the sample with x = 0.98 was obtained at a magnetic field of 2 T. Meanwhile, all the samples exhibit a significant increase in the half-height width of - ΔS M reaching approximately 35 K, increased by more than 41% compared with that of the reference sample prepared by arc melting. The broadened temperature range originates from the lattice distortion induced by the ball milling process. Our work indicates that La(Fe,Si) 13 alloys with relatively large - ΔS M and wide transition temperature range can be simultaneously obtained around room temperature by optimizing the composition and the ball milling process. • A series of La 1.4 Fe 11.8- x Co x Si 1.2 alloys were prepared by the high-energy ball milling and annealing treatment. • The - ΔS M of the sample with x = 0.98 reaches 4.0 J kg−1 K−1 around the room temperature under a magnetic field of 2 T. • All the samples exhibit a significant increase in δT FWHM reaching approximately 35 K due to the lattice distortion induced by the ball milling. [ABSTRACT FROM AUTHOR]