Coercivity enhancement in Pr9.5Fe83Zr2B5.5 magnetic nanomaterials

Abstract

The coercivity of Pr2Fe14B/α-Fe magnetic nanomaterial has been drastically improved from 6.8 kOe to 26 kOe by the diffusion of the Pr68Cu32 alloy. Pr68Cu32 alloy reacts with α-Fe to form boundary phases among Pr2Fe14B grains. The boundary phases have weak magnetic properties and have a thickness comparable to the domain wall thickness of Pr2Fe14B phase. So boundary layers are very effective in pinning the motion of domain walls, leading to an increased coercivity. The coercivity of this material at 160 °C is improved from 2.7 kOe to 10 kOe by diffusion treatment.

Coercivity enhancement by grain refinement for anisotropic Nd 2 Fe 14 B-type magnetic powders

“…The coercivity of HDDR powders is enhanced from 920 to 1440 kA/m after the modification treatment due to the microstructural changes. The high coercivity of the modified powders is comparable to that of HDDR powders obtained by the diffusion method of Nd-Cu or Pr-Cu alloys [12][13][14]. The refinement of the Nd 2 Fe 14 B grains using HDDR process has a great advantage in the fabrication process as compared to the alloy diffusion method.…”

“…The refinement of the Nd 2 Fe 14 B grains using HDDR process has a great advantage in the fabrication process as compared to the alloy diffusion method. Morimoto et al also prepared anisotropic Dy-free Nd 14 Fe 80 Zr 0.1 Al 2 Cu 0.1 Ga 0.5 B 6.2 powders with high coercivity (1590 kA/m) by conventional HDDR process, but the remanence is merely 1.22 T [24].…”

“…The coercivity of HDDR powders can be enhanced by diffusion treatment using the Dy compounds [11], but adding Dy raises the costs of the raw materials. A boundary diffusion treatment was developed with Nd-Cu and Pr-Cu eutectic alloys as diffusion agents to improve the coercivity of HDDR powders [12][13][14]. However, the coercivity enhancement is at the cost of remanence deterioration, and the diffusion treatment also increases the costs of the powders.…”

Coercivity enhancement in Dy-free Nd–Fe–B sintered magnets by using Pr-Cu alloy

“…Such diffusion treatment has been tested in hydrogenation-disproportionation-desorptionrecombination (HDDR) powders, melt-spin ribbons, hot-deformed magnets, etc., and has been proven to be very effective in coercivity improvement. [17][18][19][20][21][22][23][24] Therefore, we extend this diffusion (doping) technique into sintered magnets.…”