Ferromagnetic properties of fcc Gd thin films

Abstract

Magnetic properties of sputtered Gd thin films grown on Si (100) substrates kept at two different temperatures were investigated using X-ray diffraction, ac magnetic susceptibility, and dc magnetization measurements. The obtained Gd thin films have a mixture of hcp and fcc structures, but with their fractions depending on the substrate temperature TS and film thickness x. Gd fcc samples were obtained when TS = 763 K and x = 10 nm, while the hcp structure was stabilized for lower TS (300 K) and thicker film (20 nm). The fcc structure is formed on the Ta buffer layer, while the hcp phase grows on the fcc Gd layer as a consequence of the lattice relaxation process. Spin reorientation phenomenon, commonly found in bulk Gd species, was also observed in the hcp Gd thin film. This phenomenon is assumed to cause the magnetization anomalous increase observed below 50 K in stressed Gd films. Magnetic properties of fcc Gd thin films are: Curie temperature above 300 K, saturation magnetization value of about 175 emu/cm3, and coercive field of about 100 Oe at 300 K; features that allow us to classify Gd thin films, with fcc structure, as a soft ferromagnetic material.

Hydrogen Absorption in Gd Thin Films

“…4 are obtained in fact for two different samples deposited under the same preparation conditions. Results showed that the Gd thin film grows in a mixture of f cc and hcp phases [21] as indicated in Fig. 4.…”

Magnetic ordering temperature of nanocrystalline Gd: enhancement of magnetic interactions via hydrogenation-induced “negative” pressure

“…Note that most reports on lattice-expanded Gd are on thin-film specimen, where the level of control (regarding the quantity of expansion) is rather limited. For thin Gd films, the saturation magnetization was found to drop with increasing unit cell size 1 (strained hcp phase) or when obtaining Gd in other structural modifications ( fcc ) 26 . For a hydrogenated bulk specimen with rather large grains, strain and structural factors of thin films leading to the M s decrease are eliminated.…”

Магнитокалорический эффект в микропроводах Gd

“…Поскольку оксиды гадолиния имеют чрезвычайно низкую температуру Кюри и не могут объяснять пика энтропии при 312 K [17], можно было бы принять во внимание сосуществование в микроструктурах двух ферромагнитных фаз гадолиния hcp и fcc [11]. Однако температура Кюри fcc-фазы составляет 280−285 K [11] (т. е. меньше, чем температура Кюри основной hcp-фазы), и поэтому наличие этой метастабильной фазы не может объяснять пик энтропии при 312 K.…”