Soft Magnetic Properties of High-Resistive CoBN/AIN Multilayers

The magnetic and structural properties of multilayered CoBN/AIN films prepared by sputtering were investigated with the intention of creating film suitable for application in micromagnetic devices operating at high frequencies. A CoBN single-layer film has a resistivity ¿ of about 340 ¿¿-cm, a Bs of about 10.3 kG, and perpendicular magnetic anisotropy. CoBN/AIN multilayer films, even when the AIN layer thickness is about 3Ã…, exhibit soft magnetic properties (Hc≪1 Oe and ¿≫500) for a variety of layer thickness combinations. SEM observations suggest that the soft magnetic properties of the multilayer films originate in their in-plane uniaxial anisotropy and in the fine grains in the CoBN layers. The magnetostriction of multilayer films ranged between ±1×10^-6, and the anisotropy field was over 15 Oe. Although film thicknesses exceeded 2 ¿m, a high permeability ¿ was maintained, even at frequencies close to 300 MHz.