Microstructure and magnetic properties of iron nitride granular thin films obtained by oblique RF reactive sputtering

A series of iron nitride nano-crystalline granular thin films with different thickness and different angle of oblique sputtering have been fabricated on Si(1 0 0) by oblique RF reactive sputtering. The microstructure and magnetic properties of these samples have been investigated. Iron nitride thin films are composed of irregular spherical particles of 3–18 nm diameters with disordered face-centered-cubic structure. These particles are embedded in the amorphous iron nitride matrix with average spacing of ∼3 nm, and the films exhibit an in-plane uniaxial magnetic anisotropy. The results show that both thickness of iron nitride thin films and oblique angle have important effects on the magnetic properties of the films and magnetic resonant frequency of the films can also be tailored by these two factors. The in-plane uniaxial magnetic anisotropy fields of samples deposited for 30 min can be adjusted from 156 to 360 Oe by increasing the oblique angle from 3° to 32°. As a consequence, the resonance frequencies of films continuously increase from 2.87 to 6.05 GHz.