摘要:

The magnetic and optical anisotropies observed in oblique-incidence Permalloy films show anomalousbehavior for incidence angles greater than 60° (grazing incidence). In particular, the easy axis and thedirection of greatest optical absorption are parallel to the vapor beam for incidence angles greater thanabout 70°, while they are perpendicular to this direction for smaller angles. The anomalies for grazing-incidencefilms are caused by a shape anisotropy differing from that previously found in lower angle oblique-incidencefilms. This new shape anisotropy is attributed to the elongation in the beam direction of theparticles composing the crystallite chains which are found in all oblique-incidence films; such shape anisotropyhas been directly observed by electron microscopy.

ISSN:0021-8979    

DOI:10.1063/1.2000509

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

Permalloy films are evaporated in a vacuum of10−5 mmHg in the presence of a magnetic field to achievea uniaxial anisotropy. All annealing treatments and magnetic measurements are performed simultaneouslyin a vacuum of10−8to10−7 mmHg. In a film never heated above the deposition temperature, the temperaturedependence of the uniaxial anisotropy is stronger than in bulk Permalloy, and magnetic annealingchanges the anisotropy even at temperatures below 350°C. These changes are strongly dependent on whetheror not the magnetization is aligned in the hard direction during cooling. During annealing above 400°C thecoercive force is increased, and subsequent magnetic annealing treatments exhibit kinetics similar to thoseof bulk material.

ISSN:0021-8979    

DOI:10.1063/1.2000510

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

Films which possess rotatable anisotropy have been observed. In these films, the easy direction of magnetizationcan be selected by the application of a sufficiently large magnetic field. The temperature dependenceof hysteresis and resistivity have been studied. Films have also been examined by electron diffractioncombined with partial etch techniques. It is concluded that a nickel oxide layer on the surface of the filmis essential for the existence of rotatable anisotropy. Some mechanisms that may be responsible for thisphenomenon are discussed.

ISSN:0021-8979    

DOI:10.1063/1.2000512

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

It has been observed that the magnetic anisotropy direction of certain thin Permalloy films prepared bythe thermal decomposition of nickel and iron carbonyls can be rotated through 90 deg at room temperatureby fields less than 10 oe. The experimental conditions under which these films were prepared suggest thatthis phenomenon is due to the presence of carbon. The relaxation time for the rotation of the anisotropyaxis was calculated from the time dependence of the induction and found to be 10 msec. A simple modelhas been developed which relates the anisotropy rotation to specific domain wall configurations and to theestablishment of a “directional order” among interstitial carbon atoms.

ISSN:0021-8979    

DOI:10.1063/1.2000513

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

Free oscillations of the magnetization are excited in magnetic uniaxial Permalloy films by a small dc steppulse field with less than 0.35 nsec risetime. This field is applied perpendicularly to the magnetization andin the plane of the film. The resulting damped oscillations of the magnetization are detected by a samplingoscilloscope and investigated between 500 Mc and 1200 Mc. The eigenfrequency is determined by a dc fieldparallel to the magnetization and by the orientation of the easy axis. The eigenfrequencies agree reasonablywith the ferromagnetic resonance frequencies of the same films. The damping constants&lgr;evaluated fromthe decay time of the free oscillations and from the linewidth of ferromagnetic resonance also agree fairlywell and are in the range from 100 Mc to 300 Mc. The experimental results are analyzed by means of theLandau-Lifshitz equation.

ISSN:0021-8979    

DOI:10.1063/1.2000514

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

A preliminary study has been made of the magnetic and structural properties of Permalloy films preparedby cathodic sputtering. Films of the nonmagnetostrictive Ni:Fe::81:19 composition were deposited bysputtering in argon both from solid Permalloy cathodes and from copper cathodes which had previouslybeen electroplated with Permalloy. Using a gas pressure of 100 &mgr;, with the electrode potential 3500 v and adischarge current 150 ma, a deposition rate of about 15 A/sec is obtained. When deposited in an applied fieldof 20 oe, the films display uniaxial anisotropy withHc ≈ 2.5 oeandHk/Hc ≈ 1.5. An evaluation of the uniformityof film thickness, reproducibility of coercive force, and alignment of the magnetic easy axis indicatesthat films prepared by this method would be suitable for use in planar memory matrices.

ISSN:0021-8979    

DOI:10.1063/1.2000515

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

Experimental study of magnetic thin films prepared by sputtering in a glow discharge environmentshowed that crystal structure and chemical purity, as well as particle size and surface morphology, can becontrolled. Different physical properties, including B-H characteristics, can be reproducibily obtained bythe location of the collecting substrate with respect to the characteristic zones of the glow discharge; e.g.,Crookes dark space, negative glow, positive column, etc. This is the result of variations in deposition rateand energy distribution of the material arriving at the substrate, as well as variations in intensity of electronbombardment and the consequent temperature of the substrate. Typical results on nickel and iron filmsare reported. In contrast to several reports in the literature, ferromagnetic fcc nickel films were depositeddirectly by sputtering. Completely unoriented, polycrystalline bcc Fe films were prepared in whichBr/Bs∼1,Hc∼250 oe, andBr∼20 000oe; i.e., the magnetic characteristics were quite different from those obtainedby high vacuum evaporation.

ISSN:0021-8979    

DOI:10.1063/1.2000516

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

The magnitude andsignof the conduction electron polarization in rare earth intermetallic compounds hasbeen determined with the use of NMR techniques. Large, temperature-dependent Knight shifts of theAl27NMR were found inXA12(X ≡ rare-earth ion). These observations may be explained by assuming that anegativeexchange interaction of ∼0.1 ev exists between the localizedfelectrons of the rare-earth ion andthe conduction electrons.

ISSN:0021-8979    

DOI:10.1063/1.2000367

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

We have measured the pressure dependence of theFe57nuclear magnetic resonance frequency&ngr;in ferromagneticiron from1–10 000 kg/cm2at −77°C, 0°C, and 84.2°C. From these measurements the volumedependence of&ngr;has been obtained, enabling us to correct measurements of&ngr;(T)P = 1 atmfor the effects ofthermal expansion. By making a similar correction for the effect of thermal expansion on the temperaturedependence of the saturation magnetization&sgr;, we have found that, at constant volume, the hyperfinecoupling constantAin the relation&ngr; = A&sgr;is an explicit function of the temperature. Thus, measurementsof the temperature dependence of&ngr;, even when corrected to constant volume, do not give accurately thetemperature dependence of&sgr;. The results of a theory based on Stoner's collective electron model for thedelectrons are presented to account for the temperature dependence ofA.

ISSN:0021-8979    

DOI:10.1063/1.2000368

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

The Mo¨ssbauer effect, the resonant absorption of nucleargamma rays in solids, may be used to obtain the hyperfinestructure ofFe57in magnetic materials. Experiments are performedby observing the absorption bystableFe57of the 14.4-kevgamma ray coming from a source which containsradioactiveFe57produced by the decay ofCo57. The experiments are notlimited to naturally iron-bearing materials; other substances canbe studied, provided only, that small amounts of cobalt can beintroduced into lattice sites of interest. The magnetic momentsof the ground and first excited states ofFe57are known andmake possible direct determination of the field at the iron nucleusonce the hyperfine structure has been measured. The magneticfield at iron nuclei has been determined in the ferromagnetictransition metals (Fe 3.42×105 oe,Co 3.12×105 oe,Ni 2.80×105 oeat 0°K), but no hyperfine structure has been observed down to4°K in the antiferromagnetic transition metals, Mn and Cr. Inthe case of yttrium-iron garnet the fields at the iron atoms in thetwo types of sites have been obtained (tetrahedral3.9×105 oe,octahedral4.7×105 oe). The most complete analysis so far hasbeen made inFeF2where the magnetic field in the antiferromagneticstate(HT = 0 = 3.40×105 oe)and the quadrupole splittingin the paramagnetic state (31.2 Mc/sec) have been obtained.Other materials under investigation are the iron oxides andsome ferrites, where, for trivalent iron, fields in the vicinity of5.0×105 oehave generally been found.

ISSN:0021-8979    

DOI:10.1063/1.2000369

出版商:AIP    

年代:1961

数据来源: AIP