Switching fields of high-resolution magnetic force microscope tips coated with Co, Co₇₅Pt₁₀Cr₁₅, Co₇₅Pt₂₅, and Co₅₀Pt₅₀ films

Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan

^a Corresponding author: futamoto@elect.chuo-u.ac.jp

Published online: 3 July 2014

Abstract

Magnetic force microscope (MFM) tips are prepared by coating Si tips of 4 nm radius with Co, Co₇₅Pt₁₀Cr₁₅, Co₇₅Pt₂₅, and Co₅₀Pt₅₀ (at. %) films of 20 nm thickness at 300 °C. The effects of coating film material on the spatial resolution and the switching field are investigated. Higher resolutions are observed in the order of Co₇₅Pt₁₀Cr₁₅ < (Co₅₀Pt₅₀, Co₇₅Pt₂₅) < Co. The Co-coated tip shows the highest resolution of 7.3 nm, which seems to be depending on a high detection sensitivity related with the magnetic moment of Co material. The saturation magnetization increases in the order of Co₇₅Pt₁₀Cr₁₅ < Co₅₀Pt₅₀ < Co₇₅Pt₂₅ < Co. Higher switching fields are observed in the order of Co < Co₇₅Pt₁₀Cr₁₅ < Co₇₅Pt₂₅ < Co₅₀Pt₅₀. The Co₅₀Pt₅₀-coated tip shows the highest switching field of 1.675±0.025 kOe, which is due to a high coercive field of the magnetic film involving L1₁ ordered phase with high magnetocrystalline anisotropy energy. The coercive field is recognized in the order of Co < Co₇₅Pt₁₀Cr₁₅ < Co₇₅Pt₂₅ < Co₅₀Pt₅₀. A tip prepared by coating Co₅₀Pt₅₀ film which has high resolution and high switching field is useful for MFM observations of high-density recording media and permanent magnets.