Low spin reorientation transition temperature, high coercivity, Nd2(Fe,Co,Cr)14B based hard magnetic nanoparticles

We have synthesized high coercivity Nd
2
Fe
10.5
Co
2
Cr
1.5
B magnetic nanoparticles through a green and low cost mechanochemical method. The coercivity (H
C
) of isolated Nd
2
(Fe
10.5
Co
2
Cr
1.5
)B nanoparticles and nanoparticles embedded in a CaO matrix was found to be 11.3 kOe and 9 kOe, respectively. The thermal coefficient of remanence (α (Mr)) and coercivity (β (H
C
)) of these nanoparticles after removal of CaO, measured from room temperature to 400 K, was found to be -0.0015 and -0.0065, respectively. These nanoparticles exhibit the spin reorientation transition temperature (T
SR
) of ∼89 K, which is ∼46 K less than that of bulk Nd
2
Fe
14
B magnets, hence, more attractive for cryogenic applications.