摘要:

Microstructure and magnetic properties of Mn‐Al multilayered films are studied by high‐resolution transmission electron microscopy (TEM), x‐ray diffraction, and vibrating sample magnetometry to investigate the origin of ferromagnetism. High‐resolution TEM images show that the Mn‐Al interface is sharp and that the crystal lattice is continuous across the interface. The possibility of ferromagnetic alloy formation is ruled out for explaining the origin of ferromagnetism. The magnetic measurements are made on films with various layer thicknesses and numbers of layers. The saturation magnetization increased as the number of interfaces increased. Magnetic anisotropy differs between films with odd and even numbers of layers. These results suggest that the ferromagnetic regions are located around the Mn‐Al interfaces, where large strain and/or stress exists.

ISSN:0021-8979    

DOI:10.1063/1.353254

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Existing techniques for characterization of longitudinal recording media using remanence measurements are extended to perpendicular media, in particular to Alumite, and correction for demagnetizing fields is taken into account. It is found that these techniques have limited value because of the sensitivity of the analysis to the correction factor used. Measurement of the recoil lines is investigated as an alternative method of probing the reversal processes.

ISSN:0021-8979    

DOI:10.1063/1.353255

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

A Pd/Co double layer has been grown epitaxially in ultrahigh vacuum on a Pd(111) single crystal, with the Co in the shape of a wedge of thickness varying from 0 to 10 monolayers (ML). The polar magneto‐optical Kerr effect has been used to make a nearly continuous set of measurements of the magnetic properties as a function of Co thicknesstCo. The coercive fieldsHcand nucleation fieldsHnshow large, well‐defined maxima attCo∼2.3 ML. Between 4 and 9 ML, we find thatHcfalls with increasing thickness according to atCo−5/2dependence. The Kerr ellipticity and Kerr rotation depend linearly on Co thickness above ∼2 ML Co, but show appreciable offsets when extrapolated totCo=0. These offsets are clear evidence of the polarization of Pd near the interfaces. Extensiveinsitugrowth studies of the structure of the films are also reported.

ISSN:0021-8979    

DOI:10.1063/1.354061

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Experimental data of the intrinsic perpendicular magnetic anisotropy energy constantKuare presented for amorphous rare earth‐transition metal (RE‐TM) Tbx(FeCo)1−xand multilayered Co/Pt thin film samples. These data were independently measured using five techniques based on torque magnetometry, the extraordinary Hall effect, and the magneto‐optic Kerr effect. In the Hall effect measurement, the external field was applied to the sample in three different ways: fixed at 45° from the film normal; rotating around the sample; and fixed along the in‐plane direction. The results obtained with these techniques agree with each other for the Co/Pt samples. However, we do find systematic differences in the measuredKufor the Tbx(FeCo)1−xsamples. For example,Kugiven by the Hall effect and Kerr effect is always larger (by up to a factor of 3) than that given by torque technique. Another interesting fact is thatKugiven by the Hall effect technique drops asxapproaches the compensation pointxcin the TM‐dominant case, but increases asxapproachesxcin the RE‐dominant case. These experimental results are explained by taking into account the canting between RE and TM subnetworks.

ISSN:0021-8979    

DOI:10.1063/1.353256

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Investigating the initial curve of various ferromagnetic materials a novel effect was found: when a specimen is demagnetized by an ac field with decreasing amplitude using a small number of cycles, the initial magnetization curve exhibits a distinct peaky structure. This structure can be explained by the Preisach model [see Mayergoyz,MathematicalModelsofHysteresis(Springer, New York, 1991), e.g., p. 1] thus providing new means of testing and applying this model using a noncyclic measurement.

ISSN:0021-8979    

DOI:10.1063/1.353257

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

X‐ray‐diffraction studies carried out on Tb0.27Dy0.73Fe2−xCox(x=0,0.5,1.2,2.0) revealed that all compositions investigated retained the C‐15 cubic Laves phase structure. Magnetization and electrical resistivity measurements were carried out in the temperature range 77–800 K. Anomalies observed in the resistivity measurements have been identified corresponding to spin reorientation transitions occurring in this system. Some of these transitions have also been observed in the magnetization data. Magnetostriction and magnetomechanical coupling coefficient were measured on samples ofx=0, 0.5, and 1.2 prepared by arc melting as well as arc melting followed by zoning using an induction furnace. Magnetostriction and coupling coefficient were found to decrease with increase in cobalt concentration. Magnetostriction data on zoned samples revealed a change in the easy direction of magnetization from [111] to [100] in the case ofx=0.5.

ISSN:0021-8979    

DOI:10.1063/1.353258

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Using radio frequency (rf) sputtering, we have prepared in presence of a static magnetic field, ferromagnetic thin films of composition (Co93Zr7)100−yREy(RE=Nd,Pr,Dy,Tb... a magnetic rare earth element). This study was performed for small amounts of RE substitution (0<y<3). These films exhibit attractive soft magnetic properties similar to CoZr alloys: low coercivity (Hc∼1 Oe), and a high saturation induction (4&pgr;Ms≳10 kG). A low in‐plane uniaxial anisotropyHkwas induced, whose magnitude depends upon the composition and the preparation parameters. Substitution by RE atoms affects essentially the &mgr; frequency‐response. Depending on the nature, the concentration of RE atoms and on the value ofHk, a high relative rotational permeability &mgr; (&mgr;’∼500–3000 at frequencies up to 500 MHz) was obtained. Also depending on RE and ony, high &mgr;‘(&mgr;‘∼400–3000 at &ngr;∼1 GHz) distributed over a very broad frequency range (&Dgr;&ngr;∼500–2500 MHz) could be measured.

ISSN:0021-8979    

DOI:10.1063/1.353259

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Ferroelectric local domain inversion occurs in LiTaO3crystals by proton exchange followed by heat treatment at temperatures just below the Curie point, thereby yielding an inversion layer at the −csurface. This article reports the domain inversion phenomenon in LiTaO3plates and the experiments performed to clarify the mechanism. Measurements of dielectric constant and electrical conductivity near the Curie temperature suggest that the pyroelectric fields induced during the cooling down period are not likely to be the main cause of the domain inversion. This experimental result is reinforced by measurements of the piezoelectric response during heat treatment, which shows that the antipolarity domain nucleates at the initial stage of heat treatment and grows gradually.

ISSN:0021-8979    

DOI:10.1063/1.354082

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The problem of calculating the free energy of a ferroelectric random copolymer is discussed in terms of a mean field model. The intrachain interactions are treated in detail, but the interchain interactions are approximated as a function only of the torsional angle at a chain segment and of an order parameter determined by averaging over the conformations of all chains. This formalism is applied to a simple model of the random copolymer of vinylidene fluoride and tetrafluoroethylene. The results of this calculation are combined with the known Curie temperatures of these copolymers to determine the magnitude of the effective interchain interaction over a range of copolymer compositions.

ISSN:0021-8979    

DOI:10.1063/1.353260

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

In general, the piezoelectric ceramic and polymer in a 1–3 type composite will have different deformations when subjected to an external field. How each component deforms, to a large extent, determines the performance of the composite. Based on the force equilibrium condition, an elastic model is introduced to analyze the strain profiles of these composites, and the theoretical results are in quantitative agreement with the strain profiles measured on several composites using a double beam ultradilatometer. The results obtained provide quantitative information on how various parameters in a composite affect the performance of the composite. Furthermore, a scheme is proposed for evaluating the strain profile of a 1–3 type composite under a hydrostatic pressure using a double beam dilatometer.

ISSN:0021-8979    

DOI:10.1063/1.353261

出版商:AIP    

年代:1993

数据来源: AIP