The fabrication and characterization of magnetic properties of Ni and Cu doped Nd-Fe-B magnets

In this study, four series of samples which are called as temperature, Cu, Ni and Ni+Cu series were produced from commercial Nd15Fe77B8 ingot. Structural properties of the produced samples were performed by X-ray diffraction and density measurements. Microstructure observations were carried out using polarized optic and scanning electron microscopes. Magnetic properties of the samples were performed by both the magnet tester and DTA-TG devices at room temperature.For samples of temperature series, it is found that the magnet sintered at 1050 ºC showed the best magnetic properties. Ni with high melting point and Cu with low melting point were doped to Nd15Fe77B8 ingot. It was seen that doping with 0.2 at.% Cu increased the density of the sample while the same amount of Ni-doping enhanced the magnetic properties of the specimen. It was also observed that Ni and Cu doping did not enter inside of main phase of Nd2Fe14B. Instead, they distributed in the intergranular phases. It was found that Ni doping increased the Curie temperature of the magnet whereas Cu doping did not significantly change the Curie temperature. Both the magnetic and mechanic properties of the magnets improved after doping with 0.2 at.% Ni+Cu. For these samples, Curie temperature also increased with the increase of Ni and Cu doping.