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

The structural and magnetic properties of DyFe_12−xTa_x compounds (with x = 0.5, 0.6, 0.65 and 0.7) have been investigated in detail using dc magnetization, differential scanning calorimetry, Mössbauer 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_sr2 for all compounds, then to easy plane at T_sr1. Both T_sr1 and T_sr2 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 ∼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.