Thermal stabilization processes on CrO2powders modified with Fe dopants

Various thermal treatment are employed on CrO2powders doped by 2.23% (by weight) of Fe and 0.30% of Sb in order to prevent the chemical degradation of the particle surface. Generally, these treatments do not influence the magnetic properties of pure CrO2powders, but in the case of CrO2doped with Fe they can produce a degradation of the magnetic properties, reducing the improvements due to the dopants. Several magnetic and structure parameters of the doped powders are examined after the thermal treatment; particularly: the coercivity, the squareness ratio, the switching field distribution, the rotational hysteresis, the X-ray diffraction peaks. The degradation of the magnetic properties is correlated to the crystal deterioration because of the Fe dopant migration. On experimental basis, suitable conditions of the thermal stabilization process are established in order to avoid an excessive reduction of the magnetic advantages produced by the Fe dopants.