We investigated the variation in the magnetic and magneto-optical properties of GdDy/FeCo films deposited by two-source magnetron sputtering. When the substrate rotation was varied, Ms and Hc were greatly altered. For a better understanding of the recording characteristics by the magnetic field modulation recording of GdDy/FeCo magneto-optical disks, the temperature dependencies of Ms and Hc were investigated for films prepared by magnetron sputtering using both GdDy and FeCo alloy targets. The magnetic properties of GdDy/FeCo films can be adjusted by changing the GdDy content. We found that the compensation temperature has a significant influence on the recording characteristics. Therefore, GdDy/FeCo films with the same compensation temperature as well as the same Curie temperature exhibit the same CNR at magnetic fields below 200 Oe, regardless of the substrate rotation rates.
Write/erase cyclability on Co-rich Pt/Co disks was studied, along with its limiting factors. Annealing experiments suggested that a decrease in CNR resulted from degradation of the perpendicular magnetic anisotropy in a Pt/Co film heated by an erasing laser beam. The main mechanism of the degradation is atomic intermixing at the interface in Pt/Co multi-layers. In the case of a Pt/Co film exposed to air, Co might be oxidized during the erasing cycles. The higher peak temperature of Pt/Co films accelerates the intermixing. Therefore, the number of cycles was increased by adding a heat-diffusive layer to the Pt/Co film in order to decrease the peak temperature. For example, Au-coated Pt/Co disks were capable of 105 cycles, on account to the lower peak temperature (430°C), whereas SiN-coated Pt/Co disks, whose peak temperature was 770°C, were capable of only 102 cycles.
Recently, Fe-based nanocrystalline soft magnetic alloys with high saturation magnetization (Bs) produced by melt-spinning and sputtering have been discovered. Most of these alloys are obtained by annealing amorphous phase, adding and consequently there is a limit to the Bs obtained by glass-forming elements. We have been studying soft magnetic alloy films with high Bs, which have nanocrystalline structures in an as-deposited state. In this paper, we describe the magnetic and structural properties of nanocrystalline Fe-M-O(M=Y, Ce) alloy films. Y or Ce and O elements in the films have a tendency to make the bcc grains finer in an as-deposited state, and also repress the growth of the grains in an annealed state caused by the existence of very fine oxide particles, less than 10 nm in size, containing Y or Ce. The highest Bs, μe at 1 MHz, and the lowest Hc values reach 1.95 T, 1200 and 0.6 Oe for a Fe85Y4O11 film annealed at 773 K for 3.6 ks.
In-situ longitudinal Kerr effect measurements were used in conjunction with ellipsometry measurements over the photon-energy range from 2.0 to 4.6 eV to investigate the magneto-optic properties of polycrystalline Co films deposited on fused quartz substrates. AFM observations and ellipsometry measurements show that Co makes islands on the substrates in early stages of deposition and that the films become continuous in an optical sense when their thickness is about 60Å. The spectral shapes of both the real and imaginary parts of wσxy show significant changes for 100-Å-thick and less than 60-Å-thick films. The dependence of the spectral shapes on the Co coverage is discussed in relation to the film structure. Below 30Å, the calculated wσxy, based for a formulas of effective dielectric tensor for a composite material containing fine magnetic particles, and using the measured dielectric constant of a 100-Å-thick Co film, agrees closely with experimental results.
Co/Cu multilayers were prepared on a glass substrate by both vacuum evaporation and sputtering methods. Pure Cu films were also prepared by the same methods. The surface morphology and resistivity were investigated in order to determine the influence of the preparation methods on the film structure. The MR ratio oscillates with the Cu layer thickness, dCu, in sputtered multilayers prepared at low Ar pressure (15 mTorr), whereas it increases monotonically with dCu in sputtered multilayers prepared at high Ar pressure (50 mTorr). On the other hand, the MR ratio oscillates with dCu only beyond 20Å in evaporated multilayers prepared at a high deposition rate (2Å/s). The MR ratio of the samples prepared at a low deposition rate (0.5Å/s) almost disappears. The AFM investigation of the multilayers and Cu films indicates the existence of a rumpling of the layered structure, with a waving period of 100Å～500Å. The fluctuation of the rumpling is large in multilayers evaporated at a low rate (0.5Å/s) and small in multilayers sputtered at low pressure (15 mTorr). The difference in the MR ratio between the samples prepared by the two methods and in the different conditions is mainly due to the difference of the multilayer stacking structures.