The scanning near-field optical microscope (SNOM) is well known as a tool for observing nano-structures. On that account, a SNOM to which a certain magneto-optical (MO) measurement technique is applied, or MO-SNOM, is likely to become a powerful tool for nanometric studies on magnetism. In our study, a transmission-illumination mode SNOM with a bent optical fiber probe, which operates as a cantilever in atomic force microscopy (AFM), was employed. Incorporation of the polarization modulation technique into this system has made it possible to resolve magnetic structures with a high sensitivity of up to 1 mrad and a resolution of approximately 1/5 times the wave-length of the light source (argon ion laser: 488 nm). The behavior of polarized light in the probes, however, prevents quantitative analysis of MO effects. This paper describes an investigation into the polarization properties of the bent optical fiber probes, based on their Stokes parameters. A method for acquiring pure signals dependent on ellipticity or rotation in MO imaging is presented.

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The structures and soft magnetic properties of Fe-Al-Si-M-B (M=V, Nb, Ta) alloy ribbons crystallized from amorphous state were investigated. The ribbons were composed of bccFe(Al, Si) crystallites in the DO₃ ordered phase, with a grain diameter of less than 30 nm. These nanocrystalline alloy ribbons showed low saturation magnetostriction below 1 × 10^-6 and high effective permeability above 10,000 at 1 kHz after annealing. Soft magnetic properties were obtained in the ribbons, generally in the order of Nb > Ta=V. Fe₆₆Al₈Si₁₄Nb₃B₉ alloy ribbon showed particularly good soft magnetic properties (λ_s = 0.5 × 10^-6, μ_eff=59,000 at 1 kHz) with good thermal stability.

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