摘要:

In heteroepitaxial films grown by chemical vapor deposition, the uniaxial anisotropy required for the formation of bubble domains may be stress‐induced by lattice constant mismatch between film and substrate. The signs of the magnetostriction constants of gallium‐substituted erbium iron garnet permit stress‐induced uniaxial anisotropy to be caused by either tensile or compressive stress. The lattice parameters of desired film and substrate compositions are estimated and chemical vapor deposition conditions are given. Gallium‐substituted erbium iron garnet is a useful bubble domain material. A typical film of composition Er3Ga0. 7Fe4.3O12has the following properties: thickness 4.4 &mgr;m, magnetization 132 gauss, characteristic length 1.5 &mgr;m, temperature coefficient of bubble diameter at 300°K 3.3 percent/K°, Neel temperature 435°K. Better quality films have been realized in tension than in compression.

ISSN:0094-243X    

DOI:10.1063/1.3699401

出版商:AIP    

年代:1972

数据来源: AIP

摘要:

Epitaxial magnetic garnet films have been grown from coprecipitated oxide mixtures of the desired garnet composition and the flux (PbO or Bi203). They were prepared by the coprecipitation of the hydroxides yielding an amorphous mixture which in turn is converted to a solid solution of the mixed oxides by heating. The mixtures can be applied to the substrate in the form of a slurry in acetone or by a spray technique. The substrate is then heated above the melting point of the mixture and cooled slowly to form the film. This method offers ease of film preparation.

ISSN:0094-243X    

DOI:10.1063/1.3699402

出版商:AIP    

年代:1972

数据来源: AIP

摘要:

Epitaxial films of Ga:YIG (gallium substituted yttrium iron garnet) deposited on GGG (gadolinium gallium garnet) substrates often fracture. This is especially noticeable for the gallium compositions which are favorable for the formation of bubble domains. A consideration of the conditions which lead to fracture indicates that fracture will not take place unless film thickness is greater than the length of a Griffith crack. This conclusion has led us to modify the lattice parameter of the Ga:YIG to ensure that the Griffith crack length is larger than the thickness of the film. This has been achieved by substituting Gd or Eu for some of the Y. It has eliminated the fracture problem and yet the magnetic properties required for the formation of stable bubble domains have been retained. In this work an x‐ray diffraction technique was used for the measurement of the epitaxial strains. This technique and the results of the strain measurement will be described.

ISSN:0094-243X    

DOI:10.1063/1.3699403

出版商:AIP    

年代:1972

数据来源: AIP

摘要:

(Eu,Y)3(Fe,Ga)5012garnets have desirable magnetic properties for bubble domain applications and can be grown as epitaxial thin films on simple Gd3Ga5012substrate crystals. These films have the general formula EuRY3−RFe5−xGax012and are in the composition range of the prototype Eu.5Y2.5Fe4Ga012. Room temperature magnetization can be estimated from the expression 4&pgr;M = 1170 − 120.R − 790.x. Uniaxial anisotropy in these films results from biaxial compressive stress induced by a lattice mismatch with the GGG substrates (ao= 12.384 A˚) . Lattice parameters for films grown from Pb0‐B203fluxed melts by the LPE method are ao= 12.376 + 0.041·R − 0.015·x + 0.013·p, where p = wt.% Pb incorporated into the films. The effects of growth parameters on Ga content and Pb incorporation in these films are discussed. The Ga‐ and Pb‐contents of films are critical factors in determining magnetization and anisotropy, respectively.

ISSN:0094-243X    

DOI:10.1063/1.3699404

出版商:AIP    

年代:1972

数据来源: AIP

摘要:

Ga:YIG films which have partial replacements of Y by Gd or Eu, and which were grown on (111) and (100) Gd3Ga5O12substrates near 900°C by liquid phase epitaxy, show annealing effects in air and oxygen between 800 and 1200°C. The uniaxial anisotropy has a nearly linear variation with the film‐substrate lattice mismatch, indicating a stress‐induced anisotropy. The magnetic moment, coercivity, domain mobility, and optical absorption changes which occur as a result of annealing are also noted in this temperature range.

ISSN:0094-243X    

DOI:10.1063/1.3699405

出版商:AIP    

年代:1972

数据来源: AIP

摘要:

The temperature dependence of static magnetic bubble domain parameters have been measured in the range (0‐100°C) for a number of epitaxially grown rare‐earth garnets including the nominal compositions Er2Gd1Al.4Fe4.6012, Eu1Er2Ga.7Fe4.3012, Er1.5Eu1.5Al.4Fe4.6012, Yb2Gd1Ga.5Fe4.5012and Y1.3Eu1.7Al1Fe4012. The temperature coefficient of the bias field, H, required to collapse a bubble domain is positive at 0°C for all except the Y1.3Eu1.7garnet and it is negative or zero for all except the Er2Gd garnet at 100°C. The collapse bubble diameter decreases with increasing temperature except for the Y1.3Eu1.7garnet, where the temperature dependence is about zero. The bubble diameter decreases most rapidly in the first part of the temperature range, consistent with increases in magnetization, Ms, and decreases in domain wall energy, &sgr;w. The Eu1.5Er1.5garnet has an average bubble diameter that becomes relatively temperature independent at 100°C. In this case the negative temperature coefficient of Msnearly offsets the decreases in &sgr;w. Fixed bubble size can be obtained by having ▵Ms/Ms= ▵&sgr;w/(2&sgr;w). This condition is incompatible with ▵H = 0 except when ▵&sgr;w= ▵&sgr;Ms= 0.

ISSN:0094-243X    

DOI:10.1063/1.3699406

出版商:AIP    

年代:1972

数据来源: AIP

摘要:

The domain structures observed in low magnetization compositions of iron garnet films grown by chemical vapor deposition (CVD) on rare earth gallium garnet substrates are consistent with a recently‐developed stress model for epitaxial films1. By utilizing lattice matching, bubble domains have been formed in positive magnetostriction materials in compression as well as negative magnetostriction materials in tension. The film/substrate mismatch characteristics can be evaluated by comparing domain structures, X‐ray measurements of the strained lattice spacings, and the predictions of the stress model. Requirements and restrictions on the mismatch of film/substrate lattice constants and thermal expansions are discussed for the iron/gallium garnet system.

ISSN:0094-243X    

DOI:10.1063/1.3699407

出版商:AIP    

年代:1972

数据来源: AIP

摘要:

Hexagonal lattices of magnetic bubbles can be formed in thin platelets of uniaxial materials. They are characterized by the lattice constant and the bubble diameter; we have measured both as a function of the magnetic field normal to the platelet. These measurements were carried out for several values of the characteristic length L. They are compared with the calculations in which the energy of a bubble lattice is minimized with respect to the bubble diameter and to the lattice constant.

ISSN:0094-243X    

DOI:10.1063/1.3699408

出版商:AIP    

年代:1972

数据来源: AIP

摘要:

The mutual interaction between cylindrical domains of reversed magnetization in two separate sheets of uniaxial materials placed parallel one above the other has been studied. There are different reasons for doing this study. On the one hand the interaction between the domains(commonly called bubbles), which is quite strong in certain circumstances, can be used in magnetic bubble devices, for example to perform logical functions (section III.1). On the other hand, this study gives an impression of the cross‐talk one can expect between the domains in different sheets in a device (section III.2).

ISSN:0094-243X    

DOI:10.1063/1.3699409

出版商:AIP    

年代:1972

数据来源: AIP

摘要:

A two‐parameter variational model is used to calculate the effects of finite wall thickness on the radial and elliptical stability of cylindrical magnetic domains. The stable region of the (d/h, ℓ/h) plane is found for several values of the dimensionless anisotropy parameter q = Ku/2&pgr;Ms2. As q approaches unity from above, the region grows slightly on the upper side and then begins to contract from both above and below. The model shows a residual stability region down to q ≃ 0.75.

ISSN:0094-243X    

DOI:10.1063/1.3699410

出版商:AIP    

年代:1972

数据来源: AIP