In-situ observation of magnetization process of soft magnetic films by spin-polarized secondary electron microscopy

Capability of spin-polarized secondary electron microscopy to image response of magnetic domains to an applied dc magnetic field was investigated with a special focus on its application to soft magnetic films. The dominant artifact introduced by the field in the electron polarimetry was the precession of spins. Deflection of secondary electrons by the Lorentz force reduced the absolute count rate at the detector. However, the polarimetry was unaffected by the deflection when the Mott detector was operated at 25 kV. Owing to this, the domain structure imaged by the polarization component parallel to the field was free from disturbance. Response of domains to the applied field was successfully imaged for a high permeability alloy film (FeRuGaSiHf) and a permalloy (FeNi) film with uniaxial anisotropy. The field strength used in demonstrating the imaging capability, 12.6 Oe (1000 A/m), is sufficient for most soft magnetic materials research.