Doping is a technical term used to incorporate impurity up to a concentration till band gap of the host material does not change. The impurity atoms are chosen to have electrons in the outermost orbit one more or one less so that n and p type material could be formed. These impurity atoms act as electrically active centers only when the radius of the impurity atoms are same as the atoms of the host material. For n or p type doping, concentration should be of ppm level. At much higher concentration, a new alloy may be formed which has different band gap. Now come to your question. You have not mentioned the host material nor the impurity except that impurity is magnetic. One can not say anything about impurity effect without knowing whether band gap will be same or different after putting impurities. Whether impurity will produce electrically active centers or a new alloy will be formed. Since you are putting impurity which is magnetic material one can assume it to be metallic. In case of alloy formation, conductivity may increase due to reduction in band gap. If n or p type doping is obtained then also conductivity will increase.