Physical and Magnetocaloric Properties of TbPdAl2 and the Ferromagnetic Solid Solution Tb1-xLuxPdAl2 (x=0.1-0.9)

摘要

TbPdAl2 and the solid solution Tb1-xLuxPdAl2 (x = 0.1-1) have been synthesized via arc-melting techniques using the elements as starting materials and crystallize in the orthorhombic MgCuAl2-type structure (Cmcm). As expected, the unit cell volumes decrease due to the lanthanide contraction from the Tb to Lu compounds, thus showing Vegard behavior because of the differences of the ionic radii of the trivalent rare-earth cations. TbPdAl2 orders ferromagnetically below T-C = 85.5(5) K and shows partial magnetic saturation already at low fields. The magnetic phase transition has been additionally investigated by heat capacity measurements, showing a broadened lambda anomaly at T-HC = 83.2(1) K. The electrical resistivity is almost linear above T-C, indicating dominant electron-phonon interactions. Below the ordering temperature, electron-spin wave scattering with a rho similar to T-2 behavior is evident. In the solid solution Tb1-xLuxPdAl2 (x = 0-1), the ferromagnetic Curie temperatures decrease in a linear fashion with increasing Lu content. Investigations of the magnetocaloric properties of TbPdAl2 obtained a maximum magnetic entropy change of -Delta S-M(max) = 1.2, 2.2, 3.1, and 3.6 J kg(-1) K-1 for the field changes of Delta H = 10, 20, 50, and 70 kOe, respectively. The rather low values are caused by entropy losses due to hysteresis behavior. The relative cooling power for TbPdAl2, therefore, also exhibits comparably low values of 32, 81, 142, and 178 J kg(-1).