I think helium is used for its low kinematic viscosity. That lets the R/W head fly closer than, for example, air. The other inert gases (Ar, Ne, etc.) have KV

I think helium is used for its low kinematic viscosity. That lets the R/W head fly closer than, for example, air. The other inert gases (Ar, Ne, etc.) have KV values higher than air and would give no advantage. He is better for thermal reasons, too.