Variable-field magnetic force microscopy.

A new variable external field magnetic force microscope is introduced here. The most outstanding feature of the system is its capability to perform stable images under a variable external magnetic field that can be applied both in in-plane and out-of-plane directions. The performances of the microscope are illustrated for four different suitable selected samples: highly oriented pyrolytic graphite, longitudinal magnetic storage media, FePt thin films with in-plane anisotropy and Ni nanowires with axial easy axis embedded on a ceramic matrix. The use of this variable-field magnetic force microscope as a magnetic writing-reading technique is also shown in this contribution.