hesela.devMagnetic anisotropy
Magnetic anisotropy is the dependence of magnetic energy or response on the direction of magnetization.
Preferred directions can arise from crystal structure, grain shape or stress; magnetocrystalline anisotropy is only one contribution [1]. Anisotropy energy density, usually expressed in J/m3, is not itself a switching field or coercivity.
In a simplified zero-field uniaxial-grain model, the reversal barrier is K_u times V, where V is grain volume; dividing by k_B T gives a dimensionless stability factor [2]. Perpendicular media need the appropriate easy-axis orientation as well as isolated grains. Experiments on FePt intermediate layers show that improving grain morphology need not improve perpendicular anisotropy [3].
Relations
- related
- pmr, hamr, superparamagnetic-limit, magnetic-thermal-stability-factor, magnetic-recording-trilemma
Citations
- Moskowitz: Magnetic Anisotropy, Institute for Rock Magnetism (1991 guide)
- Evans et al.: Thermally induced error: density limit for magnetic data storage (2012), doi:10.1063/1.3691196
- Dong et al.: Columnar structured FePt films epitaxially grown on large lattice mismatched intermediate layer (2016), doi:10.1038/srep34637
Sources & caveats
- IRM supplies general magnetic background; its rock-specific values are not HDD media parameters.
- Dong et al. report thin-film experiments, not a commercial-drive lifetime study.