Magnetic domain structure of the ferrimagnetic (001) NiCo2O4 film with perpendicular magnetic anisotropy

• Growth of the ferrimagnetic (100) NiCo 2 O 4 film with perpendicular magnetic anisotropy. • Observation of magnetic domain structure with magnetic field, temperature, or time. • Creation and expansion of worm-like magnetic domains with a few micrometer size. • Indistinctive changes of magnetic domain structure with temperature and time. A 65-nm thick epitaxial (001) NiCo 2 O 4 film that has metallic and ferrimagnetic properties at room temperature was grown on a (001) MgAl 2 O 4 substrate. Evolutions in magnetic domains of the ferrimagnetic (001) NiCo 2 O 4 film with perpendicular magnetic anisotropy were observed using polar magneto-optical Kerr effect microscopy with changes in magnetic field, temperature, or time. The magnetic domain structure in the magnetic field exhibited noticeable changes around a coercive field; whereas, its change in temperature or time at a fixed magnetic field was indistinct. This suggests that the ferrimagnetic (001) NiCo 2 O 4 film has a relatively stable magnetic domain structure in comparison with Co alloy films with perpendicular magnetic anisotropy and fast domain wall motion. Conclusively, the magnetic domain variation in the NiCo 2 O 4 film signified that the magnetization process at an early stage was mainly caused by domain rotation behavior rather than domain wall motion.