Calculations of Stable Domain Radii Produced by Thermomagnetic Writing

Calculations are performed to determine the stable radius of a cylindrically symmetric domain nucleated in magneto-optical films during thermomagnetic writing with a laser beam. A critical bound on domain size is calculated which determines whether or not a domain of given radius, once nucleated, will be stable. The analysis shows that for a ferromagnetic material such as MnAlGe, the domain dimensions can grow beyond the local region of material that is heated above the Curie temperature. For ferrimagnetic thin films having a compensation point T
comp
, stability depends on the difference between ambient and compensation temperatures, ΔT = T
a
− T
comp
. With ΔT ≈ 0, wall energy dominates and the critical radius can be calculated from R
c
= σ/(2MH
c
).