Magnetoelastic interactions and magnetic damping in CoFeMnSi and CoFeGaGe Heusler alloys thin films for spintronic applications.

CoFeMnSi (CFMS) and CoFeGaGe (CFGG) Heusler alloys are among the most promising thin film materials for spintronic devices due to a high spin polarization, low magnetic damping and giant/tunneling magnetoresistance ratios. Despite numerous investigations of Heusler alloys magnetic properties performed up to now, magnetoelastic effects in these materials remain not fully understood; due to quite rare studies of correlations between magnetoelastic and other magnetic properties, such as magnetic dissipation or magnetic anisotropy. In this research we have investigated epitaxial CFMS and CFGG Heusler alloys thin films of thickness in the range of 15-50 nm. We have determined the magnetoelastic tensor components and magnetic damping parameters as a function of the magnetic layer thickness. Magnetic damping measurements revealed the existence of non-Gilbert dissipation related contributions, including two-magnon scattering and spin pumping phenomena. Magnetoelastic constant B values and the effective magnetic damping parameter α values were found to be in the range of - 6 to 30 × 10 erg/cm and between 1 and 12 × 10, respectively. The values of saturation magnetostriction λ for CFMS Heusler alloy thin films were also obtained using the strain modulated ferromagnetic resonance technique. The correlation between α and B, depending on magnetic layer thickness was determined based on the performed investigations of the above mentioned magnetic properties.