High-resolution alternating magnetic force microscopy using an amorphous FeB-based tip driven by an inverse magnetostrictive effect: Imaging of the high-density magnetic recording media

Abstract

The improved spatial resolution of the alternating magnetic force microscopy (A-MFM) technique developed in this work is demonstrated using a tip coated with a very thin magnetostrictive Fe-B-based amorphous film. Its magnetization can be periodically reversed using an applied alternating current magnetic field, which leads to alternating mechanical stress at the tip end, thus affecting localized magnetization reversal via an inverse magnetostrictive effect. Spatial resolution improvement is achieved via effective reversible magnetization volume at the sharpened tip end, which promotes a decrease in the total magnetic volume and maintains sufficient sensitivity at a lower coating thickness. A-MFM uses frequency modulation induced by an off-resonant alternating magnetic force between the tip and the sample. Therefore, a magnetic force can be selectively detected near the sample surface, independent of non-magnetic interactions. Due to their smooth surfaces without crystalline grain boundaries, large magnetization, and large magnetostriction compared with those of other magnetic materials, Fe-based amorphous films are suitable for tip coating applications. A 500-kfci perpendicular magnetic recording medium (PMR) was imaged using a 6-nm thick amorphous Fe-B coated tip to produce highly resolved images with minimal detection of the wavelength of the magnetic field of less than 10 nm. Also, 1600-kfci PMR imaging was successfully achieved, with the images showing individual ∼ 15-nm bits.