Thermal behavior and magnetic properties of Co- and Cr-substituted Nd5.5Fe66Cr5Co5B18.5

In this study, we have investigated Cr- and Co-substituted Fe3B/Nd2Fe14B-based nanocomposite alloy. Samples have been prepared by using melt-spin technique in an Ar atmosphere. Crystallization temperatures have been identified by differential thermal analysis. Samples have been annealed in an evacuated quartz tube using a pressure of around 10-5 mbar following differential thermal analysis. Structural analysis has been carried out by X-ray diffraction. Coercivity, remanent ratio and maximum energy product have been found to depend strongly on the annealing temperature. Highest value of coercivity of 4.6 kOe has been obtained for the sample annealed at 923 K for 20 min. Temperature dependence of hysteresis loop below 150 K is affected by the spin reorientation temperature of Nd2Fe14B at 135 K. In the temperature range of 250-380 K temperature coefficient of coercivity is -0.21%/deg. C, which is much lower. Recoil hysteresis loops have been measured by the application of progressively increasing negative field and successive withdrawal to the remanence and found to have small recoil area and high recoil permeability, which is characteristic of exchange-biased system