Control of the growth-induced magnetic anisotropy in ferrimagnetic garnet films grown by liquid-phase epitaxy

The influence of melt composition and growth temperature T_g on the growth-induced magnetic anisotropy constant K^g_u in Bi substituted LPE ferrimagnetic garnet films has been investigated. In films grown from Bi₂O₃ based and from $\text{PbO}\text{B}{}_2\text{O}{}_3$ based melts the value of K^g_u increased upon decreasing T_g, associated with an increasing incorporation of B1. However, at given Bi content the films grown from Bi₂O₃ based fluxes generally exhibited smaller values of K^g_u than those from $\text{PbO}\text{B}{}_2\text{O}{}_3$ based melts. The addition of small amounts of Ca²⁺ to the Bi₂O₃ based melts resulted in (Y,Bi)-garnet films changing from n- to p-type electrical conductivity at a minimum value of K^g_u. Additions of Si⁴⁺ to a $\text{PbO}\text{B}{}_2\text{O}{}_3$ based melt reduced the uniaxial magnetic anisotropy of La-YIG-Ga films accompanied by a change from p- to n-type conductivity. Similarly, (Gd,Bi)-garnet films from $\text{PbO}\text{B}{}_2\text{O}{}_3$ based melts changed from n- to p-type conductivity upon decreasing T_g where K^g_u changes sign from negative to positive. From the temperature dependence of the electrical conductivity the electron and hole concentrations in some of these films were estimated suggesting that the sign change of K^g_u in the investigated (Gd,Bi)-garnet films and the minimum of K^g_u in the investigated (Y,Bi)-garnet films and (La,Y)-garnet films occur at donor-acceptor compensation. This experimental evidence led us to conclude that the growth induced magnetic anisotropy may be correlated with the presence of donor and acceptor centers in the garnet structure.     

Influence of the anisotropy field gradient on the spectra of spin wave resonance in garnet ferrite films

It is established that the spectrum of spin wave (SW) resonance in garnet ferrite films with linear depth profile of the effective anisotropy consists (unlike the spectrum of homogeneous films) of a series of high-intensity SW modes and modes of very low intensity. The distribution of resonance fields of high-intensity SW modes depends on the gradient of the effective anisotropy field. For the same film thickness, the number of these modes increases with the value of gradient.     

Epitaxially grown Bi-substituted iron garnet films for magneto-optic devices

The growth conditions and magnetooptical properties of films of Bi-substituted iron garnets are described. The chemical composition of TmBiFe-Ga garnet films grown from a PbO,B2O3flux has been determined using the radiotracer technique of chemical analysis. The maximum value of the figure of merit (Faraday rotation per unit optical attenuation) found for these films is 2.5 deg/dB at 560 nm. Annealing experiments show that the lead incorporated in these films does not appreciably influence the optical absorption. Using a flux of Bi2O3,MeO2(with Me = Si,Ce), Bi-substituted iron garnet films have been grown. For (TmBiFeGa) garnet films a value of the figure of merit of 3.5 deg/dB at 560 nm is obtained. The Faraday rotation and the optical absorption are measured in the visible for (YBiFeGa)8O12films grown on a large lattice constant substrate. The figure of merit at 560 nm was found to be 4.7 deg/dB.     

The magnetic domain structure in low anisotropy epitaxial garnet films

Single-crystal films of (YCa)₃(FeGe)₅O₁₂ garnets were prepared by the liquid phase epitaxial method on the (111) plane of Gd₃Ga₅O₁₂ substrates. These magnetic bubble domain films have comparable uniaxial anisotropy energy, cubic anisotropy energy and demagnetizing energy. A photographic technique was developed to measure the angles of inclination of the domain magnetization vectors with respect to the normal to the sample surface. Without an applied magnetic field these inclination angles were 58° and 122°. A simple stripe domain model was used to provide an explanation of the experimental results. This model can easily be extended for other types of mixed anisotropy cases.     

Epitaxial garnet ferrite films with anisotropy of the inclined easy plane type

The character of the magnetic anisotropy in epitaxial (112)-oriented garnet ferrite films has been studied. It is shown that at a certain ratio of the constants of uniaxial and orthorhombic anisotropy in these films, the anisotropy of the “inclined easy plane” type can appear. The possible application of epitaxial garnet ferrite films with the inclined easy-plane anisotropy in highly sensitive transducers of inhomogeneous magnetic fields is substantiated.     

Control of the properties of magnetic garnet films

Large numbers of magnetic garnet films having essentially identical properties can be prepared from the same melt using the conventional LPE dipping technique, in which substrate rotation rate is adjusted to compensate for the difference between the growth temperature and the objective, thereby the growth rate can be completely controlled. Melt compositional drift has been suppressed by the periodic addition of garnet oxides and flux to the melt.     

Determination of magnetic anisotropy constants for bubble garnet epitaxial films using field orientation dependence in ferromagnetic resonances

Cubic magnetocrystalline anisotropy constant K₁ as well as uniaxial anisotropy constant K_u and gyromagnetic ratio γ are precisely determined for (111) magnetic garnet epitaxial films from measurements on FMR field orientation dependence. Strict FMR conditions are derived from total free energy expressions, where the differences between magnetization direction and applied field direction are taken into consideration. By applying magnetic field in (110) plane, FMR is measured to obtain the three best fitting parameters of K₁, K_u and γ. Present analysis is compared with Cronemeyer et al's analysis. Influence of sample misalignment on measurement accuracy is also presented. Similarly, for (110) garnet films with orthorhombic magnetic anisotropy, measurements are carried out for two crystallographic planes of (001) and (110), and the four best fitting parameters of K₁, K_u, δ and γ are determined.     

Effect of lanthanum on growth-induced anisotropy in LPE bubble garnet films

Growth-induced anisotropy, Ku, in bubble garnet films containing La and Eu or Sm has been found to be anomalous compared to that produced by Eu or Sm and smaller ions such as Y or Lu. In     

Temperature dependence of the growth-induced anisotropy of Ge-substituted garnet films by resonance techniques

Ferromagnetic resonance techniques have been used to measure the growth-and stress-induced uniaxial magnetic anisotropy of LPE grown garnet films of the nominal composition Y_1.64Eu_0.10Lu_0.30Ca_0.96Ge_0.96Fe_4.04O₁₂ from 130°K to near the Curie temperature, 455°K. The longitudinal and transverse resonance fields were measured prior and subsequent to an anneal at 1453°K. The growth-induced anisotropy, K^G_u ～?0.03 × 10⁴ ergs/cm³ at 300°K, was found to be approximately 10% of the stress-induced anisotropy, and of opposite sign for these tensile films. The associated anisotropy field, $\text{2}\text{K}{}^{\mathrm{G}}{}_{\mathrm{u}}\text{M}$ exhibited a reversal of slope, with a maximum occurring at 310°K. A model which assumes the existence of a surface anisotropy is proposed to explain these observations. The temperature dependence of the cubic anisotropy, the magnetization, the linewidth, and the exchange constant have been measured also.     

Properties of Eu-Yb-Y magnetic garnet films grown by liquid phase epitaxy

Epitaxial films of Eu_yYb_zY_3?y?zFe_5?xGa_xO₁₂ have been deposited from PbO-B₂O₃ solution on (111) Gd₃Ga₅O₁₂ substrates. Saturation magnetization, characteristic length, coercivity, anisotropy and domain wall mobility are discussed in relation to film composition. The films exhibit reasonable mobilities, satisfactory quality factors and good temperature stability. The system appears to be a promising candidate for bubble device application.     

Empirical values for growth-induced anisotropy energy coefficient for designing garnet LPE films

Growth-induced anisotropy energy coefficients and their super-cooling temperature dependence, both attributed to rare-earth ion-pairs, Kⁱ_j, and αⁱ_j, are obtained by analyzing the relationship between growth temperature dependence of uniaxial anisotropy energy, K_u, and garnet compositions. Regression processes were used for analysis. Better agreements are obtained when the newly obtained Kⁱ_j and αⁱ_j values are applied to estimate growth-induced anisotropy energy for 24 garnet compositions. The ratio of calculated growth-induced anisotropy energy values to observed values is 0.98 ± 0.12, when newly obtained Kⁱ_j and αⁱ_j values are used in place of Eschenfelder's Kⁱ_j values (0.85 ± 0.24). Appropriate melt compositions, to obtain LPE garnet films with bubble properties which meet device requirements, are easily given by computer simulation using the newly obtained values.     

Parametric chaos in yttrium-iron garnet films grown from weakly dissociated solution melt

We present the results of a comparative study of the chaotic generation of parametric spin waves in yttrium-iron garnet (YIG) films grown from a standard solution melt and in the films grown from a weakly dissociated solution melt containing garnet ferrite and orthoferrite clusters. It is shown that the efficiency of magnetic chaos generation is significantly higher in the latter case.     

The transient layer in magnetic garnet films grown by liquid phase epitaxy

A thin (～ 0.1 μm) layer is formed initially during the so-called “transient” period preceding the establishment of the steady state diffusion boundary layer in the melt, when films are dipped in a horizontal plane while undergoing axial rotation. Further evidence is given for the existence of the transient as a separate and distinct growth mode as compared to steady state growth. The transient layer, which grows comparatively rapidly, nevertheless has properties virtually identical to those of the subsequently grown steady state layer, except for its higher Pb concentration.     

The measurement of the anisotropy field of cylindrical thin magnetic films

The described method for the anisotropy field measurement uses two fields HLand HT. The deviation of magnetization from the easy direction, and hence also sense signals, are proportional to these fields. The ratio of two integrated sense signals atH_{L} = 0andH_{L} neq 0reaches a certain value (∼ 2.5) with fieldH_{T} = H_{k}. In this way, Hkmay be measured by a device designed for the coercive force measurement.     

Magnetic stress anisotropy field in plated cylindrical permalloy films

An analysis is made of the magnetic stress anisotropy field Hks, arising from internal and external stress sources in plated-wire memory elements. The analysis takes into consideration circumferential composition variation and cylindrical geometry of the Permalloy film. Expressions are derived relating Hksto uniaxial film stress, average composition, and amplitude of composition variation. A result of particular importance is that even for average zeromagnetostrictive composition (ZMC) films, Hksmay still make an appreciable contribution to the total anisotropy field if the composition is not uniform. Calculated Hkscharacteristics are shown to correlate with anisotropy field changes observed in annealing experiments. Examples are given to show the importance of composition uniformity in determining the stability of the anisotropy field. The utility of the analysis is extended by the inclusion of data expressing the inverse relation between anisotropy field and easy-axis dispersion in the film.     

An optical investigation of transient layers in magnetic garnet films grown by liquid phase epitaxy

The growth of garnet films using Liquid Phase Epitaxy has led not only to materials with improved performance for bubble domain memories but to materials which exhibit improved microwave properties as well. We have investigated the optical properties of such films and found that there exist transient layers at the substrate/film interface and at the film/air interface. Our results and conclusions regarding the substrate/film interface do not agree with those of Davies et al⁽¹⁾. The discovery of a post growth lead rich layer has not been previously reported to our knowledge and has important implications for both bubble domain and optical applications of garnet films.     

Intrinsic pinning of a ferromagnetic domain wall in yttrium iron garnet films with strong uniaxial anisotropy

Movements of individual domain walls in a ferromagnetic garnet were studied with angstrom resolution. The measurements reveal that domain walls can be locked between adjacent crystallographic planes and propagate by distinct steps matching the lattice periodicity.     

Characterization of RF-sputtered garnet films

Noncrystalline garnet films of nominal composition Y₃Fe₅O₁₂ and Y₂GdFe₅O₁₂ were synthesized by RF sputtering. The AC and DC resistivity data have been discussed in line with the model of Mott and Davis where conduction occurs through excitation of carriers into localized states at the band edges and hopping at energies close to the band tails.     

Flux-gate magnetic field sensor based on yttrium iron garnet films for magnetocardiography investigations

Technical Physics Letters - A new type of f lux-gate vector magnetometer based on epitaxial yttrium iron garnet films has been developed and constructed for magnetocardiography (MCG)...     

氮氧化铪薄膜在不同衬底上的场发射性能

利用直流溅射法在Si、Zn、Ni三种不同衬底上沉积HfNxOy薄膜并测试了其场发射性能.扫描电子显微镜(SEM)显示HfNxOy薄膜表面由纳米颗粒组成,X射线衍射(XRD)说明薄膜中含有HfN和HfO2两种相.场发射测试结果显示,和金属衬底上的薄膜相比,Si衬底上的薄膜的开启电场小且发射电流密度大.文中对三种衬底上发射电流密度大小不同的原因进行了讨论.电流一时间的对应关系说明HfNxOy薄膜的场发射电流稳定.