Abstract: A method and system for interrogating a thickness of a carbon layer are described. The carbon layer is on a magnetic media having an underlayer and at least one magnetic layer on the underlayer. The carbon layer resides on the magnetic layer(s). A sample underlayer is deposited on a sample substrate and a sample carbon layer provided on the sample underlayer. The sample substrate corresponds to a substrate including the magnetic media. The sample underlayer corresponds to the underlayer of the magnetic media. The sample carbon layer corresponds to the carbon layer. A region between the sample carbon layer and the sample underlayer is free of magnetic material. The sample substrate including the sample carbon layer is exposed to light. Emitted light from the sample substrate is detected to provide a Raman spectrum. The thickness of the carbon layer is determined based on the Raman spectrum.