Amorphous CoZr Research Articles

Crystallization of amorphous Zr 1− xCo x alloys

Several new metastable Zr-Co phases were observed in a study of the crystallization of amorphous Zr 1− x Co x ribbons using differential scanning calorimetry and X-ray diffraction. The cubic structure of Zr 2Co (Ni 2Ti type) transformed into the tetragonal CuAl 2 type upon heating. The crystallization temperatures T x were analysed in terms of a model proposed earlier where the activation energy for crystallization is approximated by the formation enthalpy of a hole the size of a cobalt atom. Experimental values for the activation energy were derived from the dependence of T x on the heating rate. The difference in the concentration dependence of both series of activation energies was ascribed to a temperature-dependent configurational entropy associated with the presence of chemical short-range ordering in the amorphous Zr-Co alloys.

Sputtering of amorphous Co-Zr and Co-Hf films with soft magnetic properties

Amorphous Co-Zr and Co-Hf films produced by sputtering have been investigated. The fundamental magnetic properties, sputtering conditions for the soft magnetic properties, and annealing to obtain high permeability films have been studied. The saturation magnetization, magnetostriction of the sputtered films, and range of composition of amorphous phase have been determined. Sensitive dependence of the soft magnetic properties on Ar gas pressure has been found. Sputtering in low Ar gas pressure suppresses the formation of microcrystals in the amorphous matrix and columnar structure in the films which deteriorates the soft magnetic properties. High permeability films have been obtained by annealing and their thermal stability was studied.

Preparation and properties of coevaporated amorphous Co-Zr thin films

Co1–xZrx thin films (5<x<35) were prepared by coevaporation in a two E-beam source system on glass substrates held at 30 °C. The crystallinity of all films were monitored by x-ray diffraction techniques; the films in the composition range x⩾7.4 were found to be amorphous. Magnetization, hysteresis loop, and FMR measurements were carried out with these Co-Zr films. The saturation magnetization as a function of composition shows similar trends as in the Co-Ti thin films. The FMR spectra were rather complex with four to six modes for perpendicular resonance; the most intense mode gives a value for 4πMs close to the static data. The other modes at higher resonance fields may be caused by preferential oxidation of Zr or a large negative anisotropy induced by oxidation. Auger and ion probe profile analysis of the Co-Zr films indicated the presence of oxygen throughout the bulk of these films. SEM examination of some of these Co-Zr films showed the existence of a columnar structure, and it is possible that oxygen transport is enhanced along the column boundaries. Regions with varying degrees of oxidation are thought to be responsible for the multiple FMR modes.

Studies on crystallization and domain structure of a ferromagnetic amorphous alloy Co90Zr10

The paper presents the first results of studies on crystallization and domain structure of a new ferromagnetic amorphous alloy Co90Zr10. Amorphous Co-Zr alloys were obtained by the ″piston and anvil″ method with 20 to 45 at% of Co and 90 at% of Co. Crystallization of Co90Zr10 was studied by X-ray diffraction and differential calorimetry, as well as by transmission electron microscopy (TEM) with simultaneous heating of the material. Domain structure in the amorphous phase was investigated by the method of Lorentz. The types of structures occurring were described, domain wall widths were calculated, and the direction of changes in the parameters of the magnetic structure — caused by annealing and phase transformation — was suggested.

Thermal stability and electronic properties of amorphous Zr-Co and Zr-Ni alloys

Thermal stability and electronic properties of amorphous Zr-Co and Zr-Ni alloys