Composite magnetic recording media are described. A composite structure is a structure that is formed of multiple components. For example, a composite magnetic recording medium may include a substrate, an underlayer formed over the substrate, the underlayer defining a coating surface, and a magnetic layer formed over the coating surface of the underlayer. Composite magnetic recording media constructed according to the materials and techniques disclosed may provide dimensional flexibility while exhibiting improved physical or electromagnetic characteristics. In some examples, dimensional flexibility may be achieved by pairing a substrate greater than or equal to approximately 4000 nanometers thick with an underlayer less than or equal to approximately 890 nanometers thick.