Low-noise antiferromagnetically coupled media through the use of a superparamagnetic CoCrRu intermediate layer

A superparamagnetic CoCrRu alloy is proposed for the intermediate layer (IL) between Ru/M2 in a typical antiferromagnetically coupled media structure M1/Ru/M2 (M2: recording layer). With the presence of the IL, the exchange coupling energy (J_ex) initially increases from ∼0.09 to ∼0.10 erg/cm² and asymptotes to ∼0.056 erg/cm² when the IL thickness reaches 11 A. Due to its superparamagnetic nature, the CoCrRu IL does not introduce extra medium noise, in contrast to the ferromagnetic CoCrPtTa IL. The vibrating sample magnetometer thermal stability ratio (KV/kT) increases from 52 to 58 with a ∼7 Å CoCrRu IL, in agreement with the improved spin stand signal decay. X-ray diffraction scans indicate an improved epitaxial growth in the M2 layer when a CoCrRu IL is present. © 2003 American Institute of Physics.