A study of the anomalous field evaporation of Sm(Co0.68Fe0.20Cu0.10Zr0.02)7.5 alloy by 3D atom probe

3D atom probe analysis of the composition of a Sm(Co0.68Fe0.20Cu0.10Zr0.02)7.5 alloy was conducted by varying the probing temperature from 10.6 to 65 K and pulse fraction from 10% to 20%. It was found that the preferential evaporation of Sm occurred at 65 K, due to the very low evaporation field of Sm, 15.2 V/nm calculated by using the charge exchange model. With decreasing the specimen temperature, preferential evaporation of Sm was alleviated. The optimum analysis conditions which give reasonably good measurement of the composition were: the specimen temperature of 20 K and a pulse fraction ⩾15%. The effects of the specimen temperature and pulse fraction on the measured composition of the alloy are discussed, based on the charge exchange model.