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A series of LaFe11.8Si1.2/La65Co35 bulk composites were fabricated by spark plasma sintering (SPS) followed by diffusion annealing. The effect of sintering temperature (1073–1223 K) on the magnetocaloric and other properties of LaFe11.8Si1.2/La65Co35 bulk composites were investigated. The 1:13 phase content in all the annealed samples was ∼90 wt%. The mechanical and magnetocaloric properties of these annealed bulk composites could be improved by tuning the sintering temperature. The Curie temperature (TC) and maximum magnetic entropy change (−ΔSM)max of the annealed samples varied in the range of 211–228 K and 5.56–9.33 J kg−1 K−1, respectively. Selected samples exhibited excellent mechanical and magnetocaloric properties. The (−ΔSM)max value was 9.33 J kg−1 K−1 at TC of 217.8 K. Its maximum compressive strength (σbc)max value was 540 MPa at a strain of 3.48%, which exceeded the mechanical properties of most La–Fe–Si based bulk composites prepared by hot-pressing sintering (HPS). Thus, La–Fe–Si based bulk composites with good comprehensive properties could be obtained by combining SPS and diffusion annealing.

There is a growing demand for high coercivity of NdFeB magnets with low heavy rare earth in the emerging applications. In this work, dip-coating 0.02 g and 0.09 g TbH3 on the Tb-containing NdFeB magnet enhance coercivity at room temperature，respectively. The highest coercivity achieve about 30 kOe at room temperature after diffusion, which can apply to traction motors of electric vehicles. The magnetic field intensity distribution of magnet was analyzed by finite element method. Microstructures show TbH3 coat contents and original composition of NdFeB magnet influences the formation of Tb-rich shell and grain boundary phase, and determine finally diffusion depth and Tb concentration. The Tb atoms diffuse into the interior of the magnet, forming a network Tb-rich shell existed around Nd2Fe14B grains, resulting in the coercivity enhancement.

Diffusion process by Nd-Al and Pr-Al alloys was compared and investigated in Nd-Fe-B thin films. Enhanced coercivity 2.06T and good squareness was obtained by using Pr85Al15 and Nd85Al15 alloys as diffusion sources. But the coercivity of diffusion-processed thin films by Pr70Al30 and Pr55Al45 alloys decreased to 2.04T and 1.82T. High ambient coercivity of 2.26T was achieved in diffusion-processed thin film by Nd70Al30 leading to an improved coercivity thermal stability because Nd2Fe14B grains were enveloped by Nd-rich phase as seen by transmission electron microscopy Nd-loss image. Meanwhile, microstructure-dependent parameters α and Neff were improved. However, high content of Al in diffusion-processed thin film by Nd55Al45 lead to degraded texture and coercivity.

Interstitial effects of B and Li on the phase transition and magnetocaloric effect in Gd2In alloys had been studied. The antiferromagnetic (AFM) - ferromagnetic (FM) phase transition was found to be of first-order nature while ferromagnetic - paramagnetic (PM) phase transition was of second-order nature in B- or Li-doped Gd2In alloys. AFM-FM phase transition temperature was increased while FM-PM phase transition was decreased with more doping concentrations. During AFM-FM phase transition, the slope of temperature-dependent critical field (μ0Hcr) was increased by increased doping amounts. The magnetic entropy changes under small field change were enhanced by B and Li addition, which showed the beneficial effects of B and Li additions.

Nd2Fe14B-type permanent magnets have been widely applied in various fields such as wind power, voice coil motors, and medical instruments. The large temperature dependence of coercivity, however, limits their further applications. We have systematically investigated the magnetic properties, thermal stabilities and coercivity mechanisms of the (Pr0.2Nd0.8)13Fe81-xB6Hfx (x=0, 0.5) nanocrystalline magnets fabricated by a spark plasma sintering (SPS) technique. The results indicate that the influence of Hf addition is significant on magnetic properties and thermal stabilities of the (PrNd)2Fe14B-type sintered magnets. It is shown that the sample with x = 0.5 at 300 K has much higher coercivity and remanent magnetization than those counterparts without Hf. The temperature coefficients of remanence (α) and coercivity (β) of the (Pr0.2Nd0.8)13Fe81-xB6Hfx magnets are improved significantly from -0.23 %/K, -0.57 %/K for the sample at x = 0 to -0.17 %/K, -0.49 %/K for the sample at x = 0.5 in the temperature range of 300-400 K. Furthermore, it is found out that the domain wall pinning mechanism is more likely responsible for enhancing the coercivity of the (Pr0.2Nd0.8)13Fe81-xB6Hfx magnets.

The Ce17Fe78-xB6Gax (x=0-1.0) ribbons were fabricated by a melt-spinning technique in order to study the mechanism of the valence variation of Ce and their magnetic properties as well as improve the thermal stability of Ce-based rare earth permanent magnets. The systematic investigations of the Ce17Fe78-xB6Gax (x=0-1.0) alloys show that the room-temperature coercivity increases significantly from 352 kA/m at x = 0 to 492 kA/m at x = 1.0. The Curie temperature (Tc) increases monotonically from 424.5 K to 433.6 K, and the temperature coefficients of remanence (α) and coercivity (β) of the ribbons are better off from -0.56 %/K, -0.75 %/K for x = 0 to -0.45 %/K, -0.65 %/K for x = 0.75 in the temperature range of 300–400 K, respectively. The Ce L3-edge X-ray absorption near edge structure (XANES) spectrums reveal that there is more Ce4+ in ribbons under total electron yield than fluorescence yield as Ce has a high affinity with oxygen. The weight of Ce3+ increases while the weight of Ce4+ decreases in Ga-added alloys. The refined grain size and a more uniform microstructure are mainly attributed to the improved magnetic properties and thermal stability with Ga doping. This paper may serve as a reference for further developing the so-called gap magnets and the effective utilization of the rare earth resources.