Low Damping Parameter Research Articles

Deposition of Crystalline GdIG Samples Using Metal Organic Decomposition Method

Fabrication of high quality ferrimagnetic insulators is an essential step for ultrafast magnonics, which utilizes antiferromagnetic exchange of the ferrimagnetic materials. In this work, we deposit high-quality GdIG thin films on a (111)-oriented GGG substrate using the Metal Organic Decomposition (MOD) method, a simple and high throughput method for depositing thin film materials. We postannealed samples at various temperatures and examined the effect on structural properties such as crystallinity and surface morphology. We found a transition in the growth mode that radically changes the morphology of the film as a function of annealing temperature and obtained an optimal annealing temperature for a uniform thin film with high crystallinity. Optimized GdIG has a high potential for spin wave applications with a low damping parameter in the order of 10−3, which persists down to cryogenic temperatures.

Magnetic damping and spin polarization of highly ordered B2 Co2FeAl thin films

Epitaxial Co2FeAl films were synthesized using the Biased Target Ion Beam Deposition technique. Post annealing yielded Co2FeAl films with an improved B2 chemical ordering. Both the magnetization and the Gilbert damping parameter were reduced with increased B2 ordering. A low damping parameter, ∼0.002, was attained in B2 ordered Co2FeAl films without the presence of the L21 Heusler phase, which suggests that the B2 structure is sufficient for providing low damping in Co2FeAl. The spin polarization was ∼53% and was insensitive to the chemical ordering.

Interfacial perpendicular magnetic anisotropy and damping parameter in ultra thin Co2FeAl films

B2-ordered Co2FeAl films were synthesized using an ion beam deposition tool. A high degree of chemical ordering ∼81.2% with a low damping parameter (α) less than 0.004 was obtained in a 50 nm thick film via rapid thermal annealing at 600 °C. The perpendicular magnetic anisotropy (PMA) was optimized in ultra thin Co2FeAl films annealed at 350 °C without an external magnetic field. The reduced thickness and annealing temperature to achieve PMA introduced extrinsic factors thus increasing α significantly. However, the observed damping of Co2FeAl films was still lower than that of Co60Fe20B20 films prepared at the same thickness and annealing temperature.

Magnetization relaxation and structure of CoFeGe alloys

The magnetic relaxation of 10 and 50 nm thin films of (CoFe)100−xGex (0 at. %≤x≤35 at. %) alloys was investigated by broadband ferromagnetic resonance (FMR) experiments. 10 nm thin films exhibit a significant two magnon contribution to the FMR linewidth. The 50 nm films exhibit very low damping constants of α≈0.0025 and relaxation rates as low as 33 MHz in the composition range of 20 at. %≤x≤30 at. % Ge after annealing. Structural characterization revealed B2 order for these compositions. First principles calculations confirm a pseudogap in the minority channel for B2 ordered (CoFe)75Ge25 which may cause the low damping parameters and high ΔRA in CoFeGe based current perpendicular to the plane giant magnetoresistance spin valves.

Tailoring magnetism in CoNi films with perpendicular anisotropy by ion irradiation

This paper reports on the influence of ion irradiation on the magnetic properties of Co∕Ni multilayers with perpendicular magnetic anisotropy (PMA). This material is a very promising candidate for ultrahigh density spintronic applications since it exhibits high polarization and low damping parameters. We show that PMA can be tailored in a controlled way by using uniform He+ ion irradiation or focused Ga+ ion beam.