Angular dependence of switching field measured on maghemite recording particles

Abstract

The switching field, H 0, required to reverse the magnetic moment of an elongated single-domain particle, depends on the angle θ between applied field and magnetization axis of the particle, in a way related to the reversal mode. A macroscopic method based on measurements of induced remanent magnetizations was used to reveal the angular dependence of the switching field for acicular γ-Fe 2O 3 recording particles. Separate data were obtained for four particle fractions of differing coercive force. For the particles investigated reversal is most readily achieved when the field is applied at low angles to the easy axis, as is expected when the magnetic moments are reversing by incoherent rotation of the atomic spins. Furthermore, it appears that the relative increase of H 0( θ) for high θ is smaller for particles of higher minimum switching field.