Magnetic properties and transformation of crystal structure in the ErFe2-ErAl2 system

The modification of structural properties and magnetic behaviour of the ErFe2-xAlx Laves phase intermetallic compounds have been studied while changing the Al content in the range 0.36 <= x <= 1.5. Powder X-ray diffraction study at room temperature showed the formation of the cubic C15 structure, in the samples with Al content of 0.36 <= x <= 0.75 and 1.4 <= x <= 2.0. For the intermediate compositions with 0.75 <= x <= 1.4, the hexagonal C14 structure is observed. Magnetic and magnetocaloric properties of polycrystalline ErFe2-xAlx intermetallic compounds were investigated experimentally using magnetic and heat capacity measurements. The Curie temperature T-C decreases from 275 to 28K as the Al content increases from x = 0.36 to x = 1.5, respectively. Magnetization measurements in strong magnetic fields showed the complex mechanism of magnetic saturation in the studied compounds. Under an external field change from 0 to 2 T, the maximum entropy change is 6 J/kg K at T = 28K for the composition with x = 1.5. The minimum in the concentration dependence of the magnetic entropy change is observed in the vicinity of x equal to 1.25. Regularities of variations of magnetocaloric properties of ErFe2-xAlx intermetallic compounds with increasing Al content are discussed from the point of view of their both structural and magnetic states. (C) 2015 AIP Publishing LLC.