Micromagnetic analysis of remanence and coercivity of nanocrystalline Pr–Fe–B magnets

Nanocrystalline exchange coupled [formula omitted] single-phase and [formula omitted] two-phase magnets containing 20 vol % α-Fe were produced using mechanical alloying. Micromagnetic finite element simulations were used to analyze the temperature dependence of the magnetic properties. In the single-phase exchange-coupled magnet a significant enhancement of the remanence [formula omitted] was achieved at room temperature. A further enhancement of the remanence was observed in two-phase α-Fe containing magnets reaching a remanence of [formula omitted] The corresponding values of the coercive field are [formula omitted] and [formula omitted] for the single-phase magnet and the two-phase magnet, respectively. Remanence enhancement becomes more effective with increasing temperature, compensating the decrease of the saturation polarization. In the two-phase magnet the remanence increases from [formula omitted] to [formula omitted] as the temperature is increased from 200 to 300 K. Micromagnetic calculations clearly show that the increase of the exchange length with increasing temperature improves the effective coupling between the [formula omitted] and the α-Fe phase. The decrease of the coercive field with increasing temperature has to be attributed to the temperature dependence of the anisotropy field.