Temperature gradients influencing the hysteresis of ferromagnetic nanostructures (Vol. 49, No. 1)

For future data storage technology, in which downscaling of magnetic bit unit sizes is crucial, heat-assisted magnetic recording (HAMR) is one key technology to ensure the writability for magnetic bits. It relies on a laser heating pulse to lower the coercive field HC of the magnetic bit unit. Here, we investigated the temperature- and temperature gradient-dependent switching behaviour by HC measurements of individual, single-domain CoNi and FeNi alloy nanowires via measurements of the magneto-optical Kerr effect. While the switching field generally decreased under isothermal conditions at elevated temperatures, temperature gradients (ΔT) along the nanowires led to an increased switching field up to 15 % for ΔT = 300 K in Co₃₉Ni₆₁ nanowires. We attribute this enhancement to a stress-induced contribution of the magneto-elastic anisotropy that counteracts the thermally assisted magnetization reversal process. Our results demonstrate that a careful distinction between locally elevated temperatures and temperature gradients has to be made in future HAMR devices.

A.-K. Michel and 12 co-authors, Temperature gradient-induced magnetization reversal of single ferromagnetic nanowires, J. Phys. D: Appl. Phys. 50, 494007 (2017)
[Abstract]