Z.R. Zhao

Growth and control of the microstructure and magnetic properties of sputtered Nd2Fe14B films and multilayers

Abstract The magnetic and structural properties of sputtered films of Nd17 (Fe0.9Co0.1)76B7 (NFB) and multilayers of NFB with Ag and Fe have been examined. The structure of each film was determined by small- and large-angle X-ray diffraction, and the magnetic properties were measured in a room-temperature vibrating-sample magnetometer (VSM) with a maximum field of 17.1 kOe and cryogenic VSM with a maximum field of 80 kOe. The amount and orientation of the 2 : 14 : 1 phase in the samples were found to depend strongly upon the substrate material and degree of target oxidation. The primary contaminant in most of the samples studied is a fcc phase with a = 5.110 A , tentatively identified as NdO. The direction of the easy axis (axes) of the films can be correlated with the average c-axis orientation of the 2 : 14 : 1 grains, which in turn can be controlled by the application of an external magnetic field during sample annealing and crystallization. Nearly single-phase films can be produced with a maximum room-temperature coercivity of about 6 kOe and a magnetization of about 100 emu/g. Samples containing significant amounts of NdO have coercivities up to 10 kOe, but the magnetization then drops to about 40 emu/g. The magnetic properties of the multilayers also depend stongly upon the individual layer thicknesses.

Magnetic and structural properties of Nd2Fe14B permanent‐magnet films and multilayers with Fe and Ag

Etude des effets des conditions de pulverisation sur la structure et les proprietes magnetiques de couches et de multicouches de Nd 2 (Fe 0,9 Co 0,1 ) 14 B

Magnetic properties of Fe/Nd multilayer films

Measurements are reported on the relationship between magnetic properties and microstructure in thin amorphous and crystalline Fe/Nd multilayer films. The samples, denoted by (XAFe/YANd)≡(X/Y), were prepared in a multiple‐gun sputtering chamber with a microprocessor‐controlled rotating table. For X and Y values less than about 20 A an amorphous compositionally modulated structure is obtained, with magnetic properties characterized by speromagnetic ordering associated with strong Nd random anisotropy. The net magnetization in general lies in the plane of the film. The temperature and composition dependence of the coercivity, magnetization, and transition temperatures are discussed.

Magnetism and microstructure of compositionally modulated disordered Fe/Ta films

Results are presented on compositionally modulated disordered magnetic films of the form (XAFe/YATa), as a function of the modulation wavelength λ≡X+Y. Magnetization, ac susceptibility, torque magnetometry, x‐ray diffraction, and Mossbauer measurements are used to probe magnetic transitions and microstructure. For X and Y values less than about 12 A the structure is amorphous within the layers and compositionally modulated in the direction perpendicular to the film. Films with ultrathin individual layers (1–3 atomic diameters) exhibit perpendicular anisotropy while the thicker ones have in‐plane magnetization. Spin‐glass and ferromagnetic transitions are observed and are associated with specific regions of the multilayered films.

Magnetic properties of rare‐earth transition‐metal borides

The magnetic and structural properties of quaternary RCo4−xFexB alloys with R=Nd, Sm, Er have been examined with magnetometry and x‐ray diffraction. The CeCo4B‐type phase is found for all x in Er, for x≤3 in Sm, and for x=0, 1, and 2 in Nd. Maximum coercivities have been obtained in a crystallized SmFe2Co2B sample with Hc>17 kOe at room temperature.

Magnetic properties of rapidly quenched and annealed Fe10RTi and related alloys

Magnetic measurements are reported for iron‐rich ternary alloys with the following compositions: Fe10NdxDy1−xTi (0≤x≤1), Fe10SmM (M=Ti, V, and Mo), and Fe10RV (R=Y, Gd, and Dy). The samples were prepared by splat cooling or melt spinning and selected samples were heat treated. The results of x‐ray diffraction, electron microscopy, and thermomagnetic measurements on the Fe10NdxDy1−xTi series are presented and indicate that the rapidly quenched alloys are nearly single phase and become multiphase upon heating. Magnetic measurements on the other two series show that the substitution of V for Ti increases the saturation magnetization.

Microstructure studies in Nd2(Fe0.9Co0.1)14B thin films

Abstract Large coercive fields (above 10 kOe) have been produced in thin sputtered films of Nd(FeCo)B. The films were either deposited at room temperature and heat treated or deposited onto high-temperature substrates (to about 730 °C). Transmission electron microscopy was used to study the microstructure and magnetic domain structure of the films. Correlations were observed between sputtering and growth parameters, microstructure and magnetic properties.

Permanent magnet properties of sputter‐deposited (FeCo)NdB films (abstract)

Studies have been performed on sputtered thin films of Co‐doped FeNdB alloys near the 14:2:1 composition. The films were rf sputter deposited onto mica substrates using a single bulk target of composition Fe71.5Co5Nd16.5B7. The thickness of the films ranged from 1 to 10 μm. Heat treatments were given to the samples at temperatures between 500 and 650 °C and in fields parallel to the films. The films deposited at 22 °C are amorphous with Tc =240 °C. After crystallization of the tetragonal 14:2:1 phase at 600 °C, Tc increased to 410 °C, and the room‐temperature magnetization was σs ≂100 emu/g. Films annealed at 600 °C show a coercive force Hc >10 kOe and remanent induction Bs ≂10 kG. Films deposited at 622 °C and in the presence of an in‐plane field of 1.3 kOe exhibit either in‐plane or perpendicular anisotropy depending on sputtering parameters. The sputtering conditions affect the c‐axis texturing of the films, as shown by x‐ray diffraction. Correlations have been made between film‐growth conditions, micr...