Magnetic properties of thin Ni films measured by a dc SQUID-based magnetic microscope

We have applied a scanning HTS (high-temperature superconductor) dc SQUID (superconducting quantum interference device) -based magnetic microscope to study the magnetic properties of Au/Ni/Si(100) films in the thickness range from 8 to 200 Å at T=77 K. A one-domain structure with in-plane orientation of the magnetic moment was found for film thicknesses exceeding 26 Å. A drastic decrease of the magnetization of the film was detected when the thickness is less than 26 Å.