In a method of forming a magnetoresistive sensor, first and second magnetic leads are formed. Next, a junction of magnetic and electrically conductive material is formed between the first and second magnetic leads. Finally, the magnetic and electrical conductivity of an outer shell portion of the junction is reduced to form a constricted junction comprising a magnetic and electrically conductive junction core that is at least partially surrounded by the outer shell portion. Another aspect of the present invention is directed to the magnetoresistive sensor that is formed using the method.