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 ρ of about 340 μΩ-cm, a B
_s
of about 10.3 kG, and perpendicular magnetic anisotropy. CoBN/AIN multilayer films, even when the AIN layer thickness is about 3Å, exhibit soft magnetic properties (H
_c
<1 Oe and μ>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 μm, a high permeability μ was maintained, even at frequencies close to 300 MHz.