Abstract
Ferromagnetic resonance measurements at 34 GHz were carried out to study the magnetic anisotropy field of the acicular Fe particles in the commercially available particulate metal tapes for audio recording. The value of the average anisotropy field due to the acicular shape of the oriented particles has been determined to be 603 kA/m assuming the saturation magnetization (M) of 1.72 T, 80% of bulk Fe. The axial ratio of the acicular particles is 4.8, which is in good agreement with the observed value by TEM. The linewidth of 400 kA/m along the tape length direction is four times as large as that of video Co-y-Fe2O3, tapes, which is due to a large distribution of the Fe particle axis.
