Effects of Magnetic Field Application during Growth of Metallic Recording Particles

In high density magnetic recording media, the single domain metal particles, in view of H_c and M_r are more advantageous than oxide-magnetic particles. Single domain particles of iron have been synthesized with the combination method of FeSO ₄ and NaBH₄(borohydride method) in the presence of magnetic field H₀ (0-10 kOe). According to SEM micrograph of samples, stable chains of acicular particles are formed. The magnetic characterization of samples is determined by a VSM system with 10^-2 emu accuracy. The values of χ_i, M_r, H_c and Δh_r are determined for different values of H₀. The results show that the presence of a magnetic field H₀ = 9 kOe increases M_r about 50%, the sharpness of switching field distribution (SFD) more than a factor two and the initial susceptibility about two in comparison to the corresponding results without application of H ₀. For applications of magnetic recording media, higher susceptibility and remanence magnetization causes an improvement in signal-to-noise ratio (Mallinson theory), also the narrow SFD leads to sharp pulses.