Heusler alloy replacement for Iridium (HARFIR) – running
Replacement of Iridium, more precisely, of the IrMn antiferromagnet (AFM) by appropriate Heusler alloys in magnetoresistive sensors and read heads is a key technological issue. Our aim is the theoretical investigation of Heusler alloys to understand the experimental results of our international partners and to optimise the chemical composition and structural properties in order to obtain antiferromagnets with high thermal stability and anisotropy. The calculations will be based on a combination of first-principles
and spin model simulations. A number of prior calculations based on spin models have revealed that the anisotropy of the antiferromagnet and the strength of the interface coupling between the antiferromagnet and the ferromagnet are crucial for the strength and stability of the exchange bias, and therefore for the functionality of any device based on the EB effect.
We plan to work on the Heusler alloys such as Fe2VAl, Fe2TiSi and Mn2FeAl with a ferromagnetic (CoFe) or NiFe
film on top. By using the relativistic torque method and the spin cluster expansion technique we calculate the tensorial exchange interactions and the anisotropy matrices in the AFM and
FM regions as well as at the AFM/FM interface. Such calculations will explore the range of the interactions and the importance of the isotropic, anisotropic symmetric and asymmetric
(DM interaction) parts of the exchange tensor. It is of primary importance to calculate the spin structure for various alloys depending on slight variations from the stoichiometric configuration.
Any normal operating device needs room temperature functionality. We aim to calculate thermal equilibrium properties such as the sub-lattice magnetisation using the stochastic LLG equation to enable the Néel temperature to be estimated. Furthermore we aim to calculate the temperature dependence of hysteresis curves and estimate the thermal stability of the exchange bias.
- Project owner:
- Dr. Szunyogh László (Fizika Intézet)
- Fizika Intézet (TTK-PHY)
NMP3-SL-2013-604398 Collaborative Project "Heusler alloy replacement for Iridium" (HARFIR)
Konstanzi Egyetem, Németország
Bielefeld Egyetem, Németország
York Egyetem, Anglia