Magnetic and magneto-optical properties of rare-earth transition-metal alloys containing Dy, Ho, Fe, Co

Abstract

Amorphous rare-earth transition-metal alloys of composition REl−xTMx with RE=Dy, Ho; TM=Fe,Co and 0<x<1 and Dyl−x(Fe,Co)x were prepared by evaporation. The saturation magnetization, uniaxial anisotropy, coercivity, and Faraday rotation were investigated as a function of composition and temperature. Also, the spectral variation of the Kerr rotation was measured. The magnetization data indicate a strong dispersion of the RE moments due to randomly oriented local crystal field axes. The strong turndown of the Curie temperature for the Fe-rich alloys suggests that an additional dispersion is present in the Fe subnetwork. The mean field theory was used to analyze the temperature variation of the magnetization yielding smaller TM spin values and exchange coupling constants as compared with those of the Gd and Tb analogs. The uniaxial anisotropy constant Ku for Dy-Co based alloys was found to vary with the square of the Dy subnetwork magnetization as predicted by the random single-ion theory. The anisotropy of Dy-Fe and Ho based alloys require additionally dipolar terms to account for the measured temperature dependence of Ku. The coercive field Hc follows a relation Hc ∼ K1.5u/Ms. The magneto-optical effects are primarily caused by the transition metals and therefore their compositional, temperature, and spectral dependence correspond to that of their Gd and Tb analogs. Optical recording experiments on Dy-FeCo disks yield good write and erase sensitivities and carrier-to-noise ratios up to 60 dB which are comparable to those of GdTb-Fe and Tb-FeCo disks.

Exchange coupling in the correlated electronic states of amorphous GdFe films

“…Amorphous GdFe films have been used for magnetooptical recording. [27][28][29] Renewed interest originates from the observation of all-optical magnetic switching in this type of compounds promising magnetic switching on a femtosecond time scale. [30][31][32][33] The amorphous films avoid the problem of contributions from photoelectron diffraction to the MCDXPS.…”

Spin-wave excitation and Mössbauer spectrometry of amorphous interface in Tb/Fe multilayer

“…The thermal evolution of the average hyperfine field relating to the interfacial component made it possible to estimate the Curie temperature T C = 450 K of formed alloy at the interface. This temperature corresponds to a concentration x out of iron for the amorphous alloys Fe x Tb 1−x ranging between 0.6 and 0.63 [14].…”

Effects of Tb content on the microstructure and magnetic properties of Co85−Tb Dy15 films

“…Amorphous rare-earth-transition metal (RE-TM) alloy films have special perpendicular anisotropy and have been widely studied by many investigators [1][2][3]. We have reported an as-deposited CoTb amorphous film with large perpendicular coercivity, and a nearly magnetically isotropic amorphous CoTb film could be obtained by annealing this film in vacuum at 250 C for 60 min [4].…”