Effect of Al on the structural and magnetic properties ofEr2Co17−xAlx compounds

Abstract

Powder x-ray diffraction and magnetization measurements were employedto investigate the effect of Al on the structural and magnetic properties ofEr2Co17−xAlx compoundswith 0≤x≤4. Al substitution leads to a monotonic increase in the lattice parameters and anapproximately linear decrease in the saturation magnetization. The Curie temperature isalso found to decrease with Al concentration. Large thermomagnetic irreversibility seen inthese compounds has been attributed to the domain wall pinning effect. The temperaturevariation of magnetization shows compensation points in the compounds withx = 3 and 4. The field-cooled magnetizations of these two compounds in low fields are found to benegative at temperature below the compensation temperatures, which has been explainedon the basis of the temperature variations of the exchange coupling strengths of Er and Cosublattices. The easy magnetization direction at room temperature is found to be along thec-axis in all the compounds. The first order anisotropy constant at room temperature isfound to increase with Al concentration, which has been attributed to the increase in theaxial anisotropy of both the Er and Co sublattices as a result of Al substitution.