Thermally induced magnetic switching in bit-patterned media

Abstract

We have studied the thermal variation of the switching field of magnetic islands at room temperature. A model bit-pattern media composed of an assembly of islands with 80 nm width was fabricated by sputter deposition onto a pre-patterned substrate. Using direct magnetic-contrast imaging of the islands under applied field, we extract the switching probabilities of individual islands. Based on an analytical model for the thermally activated switching of the islands, we are able to determine the intrinsic magnetic anisotropy of each island and, consequentially, a distribution of anisotropies for the island ensemble investigated. In the distribution, we identify a separated group of islands with a particularly small anisotropy. We attribute this group to islands containing misaligned grains triggering the magnetic reversal. At room temperature and slow field sweep rates, the observed thermal broadening of the switching-field distribution is small compared to the intrinsic broadening. However, we illustrate that thermal fluctuations play a crucial role at high sweep rates by extrapolating our results to technological relevant regimes. Published by AIP Publishing.

Photon correlation spectroscopy with heterodyne mixing based on soft-x-ray magnetic circular dichroism

“…More recent examples comprise the fluctuation dynamics of frustrated systems such as artificial spin-ice materials [1][2][3][4], spin and charge density fluctuations in high-T c superconductor materials [5][6][7] and a fluctuation-mediated topological phase transition [8]. Technologically, fluctuations play a decisive role for the stability of magnetic recording media where thermal activation leads to the switching of the magnetic area representing a logic bit [9]. The resulting minimum size of the magnetic grains for long-term stability gives rise to the superparamagnetic limit for the recording density [10,11].…”