Effect of Al on the structural and magnetic properties of Er2Co17-xAlx compounds

Abstract

Powder x-ray diffraction and magnetization measurements were employed to investigate the effect of Al on the structural and magnetic properties of Er2Co17-xAlx compounds with 0 <= x <= 4. Al substitution leads to a monotonic increase in the lattice parameters and an approximately linear decrease in the saturation magnetization. The Curie temperature is also found to decrease with Al concentration. Large thermomagnetic irreversibility seen in these compounds has been attributed to the domain wall pinning effect. The temperature variation of magnetization shows compensation points in the compounds with x = 3 and 4. The field-cooled magnetizations of these two compounds in low fields are found to be negative at temperature below the compensation temperatures, which has been explained on the basis of the temperature variations of the exchange coupling strengths of Er and Co sublattices. The easy magnetization direction at room temperature is found to be along the c-axis in all the compounds. The first order anisotropy constant at room temperature is found to increase with Al concentration, which has been attributed to the increase in the axial anisotropy of both the Er and Co sublattices as a result of Al substitution.