This paper presents an examination of the depth range of magnetic layers through ultra-thin carbon films by time-of-flight secondary ion mass spectrometry (TOF-SIMS). X-ray photoelectron spectroscopy (XPS) was used for comparison of TOF-SIMS. The sampling depth of TOF-SIMS is somewhat smaller than that of XPS. And also, the sampling depth obtained from this analysis is larger than that of the static SIMS (less than 1 nm) [Surf. Interf. Anal. 10 (1987) 384]. Our results suggest that the sampling depth is related to the sample structure (defects or pinholes of nanometer scale), the sensitivity of analytical tools and the emission process. (C) 2002 Elsevier Science B.V. All rights reserved.