Temperature dependent magnetic properties of Dy-doped Fe16N2: Potential rare-earth-lean permanent magnet

Using the full potential linearized augmented plane wave method, we explored the magnetocrystalline anisotropy of Dy impurity doped alpha ''-Fe16N2. Here, we considered two different Dy concentrations (1.56 and 3.125%). We also investigated the temperature dependence of the magnetic properties. The Dy site occupancy was found to be concentration dependent. The magnetic moments of Fe atoms near the Dy impurity was suppressed. However, we found a large magnetic moment in Dy atom (4.85-4.87 mu(B)). Compared with the magnetic anisotropy constant in the pristine alpha ''-Fe16N2 (0.57 MJ/m(3)), we obtained an enhanced perpendicular magnetic anisotropy. The calculated anisotropy constants in 1.56% Dy doping was 0.97 MJ/m(3) while it became 1.27 MJ/m(3) in 3.125% Dy doping. The Curie temperature in the pristine structure was about 820 K and it was suppressed to 765 K and 605 K in 1.56% and 3.125% Dy doping. At room temperature (300 K), the coercive field of 3.125% Dy doped system was enhanced almost 50% compared with that of the pure Fe16N2. We also found a maximum energy product of 50.9 MGOe for 3.125% Dy doping at 300 K. Our finding may suggest that the alpha ''-Fe16N2 can be a potential permanent magnet with a lean Dy doping.