Thermomagnetic study of the amorphous cobalt-erbium borides Co80ErxB20−x (0 ⩽ x ⩽ 4)

Calorimetric, magnetic and X-ray diffraction measurements have been used to study the magnetic susceptibility and thermal stability of Co80ErxB20−x with (0 ⩽ x ⩽ 4) amorphous ribbons. The compounds are found to crystallize in Co2B and β-Co, after precipitation of the tetragonal Co3B phase. The addition of erbium shifts up the crystallization temperature leading to the increase in the stability of the amorphous state. Magnetic susceptibility measurements show that the addition of erbium increases the Curie temperature and induces noncollinear magnetic behavior. This latter fact is explained on the basis of random local magnetic anisotropy related to the rare earth atoms in amorphous materials.