Magneto-volume effect and magnetic properties in DyFe12-xTax compounds

The structural and magnetic properties of DyFe12-xTax compounds (with x = 0.5, 0.6, 0.65 and 0.7) have been investigated in detail using dc magnetization, differential scanning calorimetry, Mossbauer effect spectroscopy (5-300 K) and high-resolution synchrotron x-ray diffraction (10-700 K). The easy magnetization directions at room temperature are along the c-axis. With decreasing temperature, the magneto-crystalline anisotropy changes from easy axis at room temperature to easy cone at T-s(r2) for all compounds, then to easy plane at T-sr1. Both T-sr1 and T-sr(2) change significantly over the ranges 158-216 K and 239-259 K with increasing Ta content (x = 0.5-0.7) respectively, while the Curie temperature is found to remain essentially unchanged with a value of similar to 540 K. Pronounced magneto volume effects have been detected at the Curie temperature while no clear anomalies are observed around the spin reorientation temperatures. Large spontaneous magnetostriction has been detected below T-c for all of the compounds.