摘要:

Amorphous YCo3films are contaminated by oxygen along a thin surface layer when exposed to air at room temperature. The field for resonance corresponding to this surface layer presents a dynamical shift with a well defined minimum. On the other hand linewidth presents a large maximum &Dgr;Hmaxas a function of temperature. After annealing in vacuum &Dgr;Hmaxdecreases and the dynamical shift is no more detected. The results obtained on a 500 A˚ thick sample are analysed quantitatively using formulas developed for the longitudinal relaxation mechanism. It is found that the results on both as deposited and vacuum annealed samples are well explained if we assume that the percentage of Co atoms in the ionic state is reduced to about one third of its value after the vacuum annealing.

ISSN:0021-8979    

DOI:10.1063/1.327268

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

An anomalous frequency independent magnetic resonance field shift has been observed in amorphous Gd.37Al.63thin film alloy. Data are reported at frequencies of 9.2, 23.0, and 34.9 GHz and over a range of temperature from 4.2 K to 100 K. Below about 50 K the magnitude of the applied field required for resonance begins to deviate significantly from the value expected from the bulk magnetization of the amorphous material. An increase in the linewidth of nearly the same magnitude as the deviation of the ’’internal field’’ is also observed. The magnitude of the resonance field shift and the change in the linewidth are both insensitive to changes in the operating frequency. It is proposed that the observed resonance field shifts can be attributed to the excitation of spinwave modes localized or ’’pinned’’ within small ferromagnetic regions. The observed increase in the linewidth is then explained within the framework of this model as being due to changes in the demagnetizing fields associated with each of the variously shaped ferromagnetic clusters.

ISSN:0021-8979    

DOI:10.1063/1.327269

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

FMR technique has been shown to be capable of detecting chemical inhomogeneities present in some amorphous GdCo films. A group of bulk modes observed when the polarizing field is perpendicular to the film plane, have been shown to correspond to absorption from regions which differ slightly in their magnetization and hence in their relative Gd or Co concentration. Such inhomogeneities seem to increase with the bias voltage. A typical result shows that Gd concentration variation is in the range 1–2 at.&percent; and which is beyond any chemical analysis used currently. These inhomogeneities increase with the bias voltage and are distributed, as it were, in the whole volume of the film in a random manner as shown by acid etching experiments. Vacuum annealing at T up to 290°C does not lead to any homogenization and argon anneal leads to a new situation with a very large in plane anisotropy besides a spin wave spectra now appears in all the samples.

ISSN:0021-8979    

DOI:10.1063/1.327270

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Spin wave resonances, observed in an amorphous Gd6.9Co74Mo12.8Ar6.3ferrimagnetic alloy film, indicate that the exchange stiffness constant, A, decreases rapidly with increasing temperature. By extension of spin‐wave theory to ferrimagnets, the temperature dependence of A has been interpreted in terms of a two sub‐network ferrimagnet.(AIP)

ISSN:0021-8979    

DOI:10.1063/1.326959

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Measurements of the magnetomechanical coupling constant, k, and the &Dgr;E effect have been made on Fe71Co9B20glassy ribbons quenched by a centrifugal spinning method. An X‐ray check of the ribbons showed no trace of crystallinity. The maximum k and &Dgr;E effect were 0.81 and more than 2.2, respectively, obtained after a field anneal of 20 kOe parallel to the width of the ribbon at 384±5°C for 15 min. This relative change in modulus is the largest known.

ISSN:0021-8979    

DOI:10.1063/1.327271

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

It is demonstrated that the vibration frequencies of a magnetized reed can be sensibly affected by a magnetic field, due to the restoring force exerted on the moving pole. A simplified theory of this effect is developed which gives reasonable agreement with experimental observations. The relative importance of the pole‐effect depends on the geometry of the reed and increases with the ratio of length to thickness. The effect decreases rapidly for higher overtones. Unlike the magnetization, the pole‐effect does not saturate but rather increases steadily in post‐saturation fields, where it is conveniently separated from the &Dgr;E‐effect on which it is generally superimposed. For the geometries typically employed in the investigation of liquid‐quenched amorphous alloys, the pole‐effect can be large for the fundamental mode and may be used to determine the temperature dependence of the magnetization. If unrecognized, on the other hand, the pole‐effect can cause anomalies in the magnitude of the apparent elastic constant, and especially in the temperature dependence exhibited in the vicinity of the Curie point.

ISSN:0021-8979    

DOI:10.1063/1.327272

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Magnetostriction &lgr;shas been measured at room temperature and 80 K in Fe100−xBx(14?x?23 at.&percent;) glasses using metal foil strain gauges. Several compositions were also studied as a function of temperature from 80 K to T ? TC. The single‐ion uniaxial temperature dependence confirmed previously for Fe80B20glass is also observed here for x=20 and 22. At lower boron concentrations departures from this expected temperature dependence are observed. The values of &lgr;s(295K) show a broad maximum of about 35×10−6at x?20 at.&percent;B. Crystallization of the glasses gives rise to a nonmonotonic temperature dependence of &lgr;s.

ISSN:0021-8979    

DOI:10.1063/1.327273

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Measurements of the velocity of sound as a function of magnetic field are presented for amorphous DyFe2and HoFe2. The samples were prepared by rapid sputtering. Measurements were taken over a series of temperatures from above to well below the magnetic transition temperatures of both specimens. In DyFe2shear waves polarized parallel to the field were observed to propagate more slowly than those polarized perpendicular to it. The velocity difference increased with decreasing temperature below the transition temperature becoming one percent of the velocity at sixty percent of the transition temperature. No such mode splitting was observed in HoFe2down to seventy percent of its transition temperature. Comparison is made with a similar room temperature measurement in a‐TbFe2and with magnetostriction measurements.

ISSN:0021-8979    

DOI:10.1063/1.327221

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Ferromagnetic resonance spectra of a series of evaporated Gd1−xFexamorphous bubble films with x ranging from 67.6 to 81.6 at.&percent; have been measured. From these spectra the g‐factor geffwas calculated. The experimentally determined values of geffagree well with those expected from Wangness formula. Of particular interest is the comparison of the anisotropy field values HKmeasured by ferromagnetic resonance and by a vibrating sample magnetometer. Whereas FMR can provide information on the anisotropy distribution in the film, VSM yields at best an average value for HK. In our experiments, several resonance peaks are in general found for a given film indicating the existence of a number of regions having different values of Hk′=HK−4&pgr;M. Interface effects on the substrate side and oxidation at the air‐film interface may result in layers of different chemical composition.

ISSN:0021-8979    

DOI:10.1063/1.327222

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The perpendicular anisotropy caused by the internal planar stress due to the substrate constraint in Gd‐Fe and Tb‐Fe sputtered films was investigated. The internal planar stress &sgr; in these films is found to be very sensitive to preparation conditions, especially to the argon pressure during sputtering, PAr. Stress is compressive for low PArand tensile for high PAr. The contribution of the stress to the total perpendicular anisotropy varies depending on PAr. Measurement of the anisotropy change before and after the removal of the substrate reveals that the predominant part of the perpendicular anisotropy originates from the internal stress due to the substrate constraint for Tb‐Fe films with a composition of around 30 at.&percent;Tb, where the magnetostriction is extraordinarily large.

ISSN:0021-8979    

DOI:10.1063/1.327223

出版商:AIP    

年代:1979

数据来源: AIP