Characterization of magnetic clustering and its effect on switching behavior and recording performance in perpendicular media

Abstract

Characterization of magnetic clustering and its effect on magnetic switching behavior and recording performance are investigated. Intergranular exchange coupling constant (Jc) of full-stack media is controlled over a wide range by applying a bias voltage (VB) to the bottom oxide layer only while the other conditions remain the same. With increasing VB up to 300 V, Hn considerably increases by 25% while Hc and Hs remain constant. Magnetic correlation length (Dn) extracted from major and minor loops is plotted with Jc values estimated from the ΔH(M,ΔM) method. Two distinct regions emerge, with lower Jc and larger Dn at VB ≤ 200 V, and with higher Jc and much larger Dn at VB > 200 V. These regions are consistent with the microstructures of biased CoCrPt-SiO2 films reported elsewhere. An increase in the intrinsic switching field distribution is also observed at VB > 200 V. Good correlation between KuV/kT and Dn2, and the increase in coherent switching behavior for media with higher VB, can be understood by the magnetic clustering effect. All the recording parameters of OW, resolution, low-frequency amplitude, magnetic core width, and SNR correlate well with Dn.

Ferromagnetic resonance analysis of internal effective field of classified grains by switching field for granular perpendicular recording media

“…[1][2][3][4] The SF distribution generally originates from the distribution of the internal effective fields H eff of the magnetic grains. H eff consists of the anisotropy field, the dipole interaction field, the self-demagnetization field, and the intergranular exchange (coupling) field.…”