Magnetic properties of amorphous thin films produced by ion mixing

We have produced several magnetic amorphous alloys by ion mixing of thin multilayer films. Our results show that the ion mixing technique is able to produce amorphous films of the various categories (transition metal-metalloid, transition metal pairs) at the composition appropriate for the appearance of magnetic ordering. A comparison of their saturation magnetization with that of related vapor quenched films suggests similar nearest-neighbor coordination in both kinds of samples

A Mathematical Analysis of the Subsidence in the Long Beach - San Pedro Area

This report presents the significant results from a mathematical study of the subsidence in the Long Beach area. The work, begun in December 1949 at the request of Mr. M.D. Hughes, Chief Petroleum Engineer, the Petroleum Division of the Long Beach Harbor Department, has been in progress for two years. During this period a large volume of physical data pertinent to the subsidence phenomena has been made available and analyzed. Additional tests suggested by the mathematical analysis have been instigated by the Petroleum Division so that a well integrated program of research has been brought to bear upon this problem

Abstract: Comparison of magnetic and crystalline profiles in He+-implanted Gd,Tm,Ga:YIG

Profiles of magnetic and crystalline properties in He+-implanted -oriented Gd,Tm,Ga:YIG were obtained using ferromagnetic resonance and x-ray diffraction techniques, respectively. Implantation was done at room temperature several degrees off axis. One series of samples was implanted with 140 keV He+ at 1.5, 3.0, 4.5, and 6.0×10^15 at. cm^−2. Another series consisted of three profiles obtained with single, double, and triple energies and doses in the range 30–140 keV and 9.0×10^14–3.0×10^15 at. cm^−2. For the highest dose the maximum changes in magnetic properties were: −3200 Oe in uniaxial anistropy Hk, a 55% decrease in magnetization M, a 65% decrease in exchange constant A, a 20% increase in damping parameter alpha, and no change in gyromagnetic ratio gamma. The maximum perpendicular strain epsilon[perpendicular] was 1.26% with a corresponding maximum rms random atomic displacement of 0.23 Å. Lateral strain epsilon|| was zero. No evidence was found for creation of extended defects. The highest dose was, at most, half of that required to produce amorphousness. Both DeltaHk and epsilon[perpendicular] had a significantly sublinear dependence on dose. The ratio of maximum DeltaHk for the 6.0 and 1.5×10^15 at. cm^−2 was 1.8 instead of 4.0. The corresponding ratio for strain was 2.6. The difference in sublinearity indicates that DeltaHk and epsilon[perpendicular] are not linearly related through magnetostriction. The equation relating DeltaHk, M, and epsilon[perpendicular] can be preserved only by invoking implantation-induced changes in Young's modulus, Poisson's ratio, or the magnetostriction

Annealing behavior of neon-implanted magnetic garnet

Ferromagnetic resonance spectra and x-ray rocking curves were used to measure the change in magnetic properties and strain with annealing temperature in the surface layer of (111)-oriented Gd, Tm, Ga substituted yttrium iron garnet films implanted with Ne+ at 190 keV. For doses below about 4×10^14 ions/cm^2, the entire implanted layer remains crystalline and magnetic. The implantation-induced strain decreases monotonically with increasing annealing temperature, falling to zero at a temperature of 1100 °C. The implantation-induced magnetic anisotropy varies with strain in the same manner as for unannealed material until the annealing temperature reaches 800 °C. For higher temperatures, the anisotropy has a value larger than that expected for unannealed material. At a higher dose, 5×10^14 ions/cm^2, the center of the implanted region is both amorphous and nonferrimagnetic. Single-crystal order and ferrimagnetism return with annealing near 500 °C. The magnetization and exchange constant decrease with increasing dose, and annealing at 1100 °C restores them to bulk values

Spin wave measurements of exchange constant in Ni-Fe alloy films

The ferromagnetic exchange constant has been measured using spin wave resonance in a number of iron-nickel alloys covering the composition range 60% to 90% nickel. The exchange constant varies smoothly from a value of 1.3 (10^-6) erg · cm^-1 at 60% Ni to an extrapolated value of 0.77 (10^-6) at 100% Ni. The data are in significant disagreement with the values published by Rusov

Annealing behavior of hydrogen-implanted magnetic garnet

Ferromagnetic resonance spectra and x-ray rocking curves were used to measure magnetic and strain profiles of Gd, Tm, Ga substituted yttrium iron garnet films implanted with H2 + at 120 keV and at doses in the range (3–80)×10^15 ions/cm^2. The maximum strain occurred at a depth of 3600 Å, reaching a value of 2.9% at 40×10^15 ions/cm^2. At the highest dose, the garnet was amorphous in that region which had highest strain at lower dose. The strain has two components, one due to damage and one due to the presence of the hydrogen atoms. The second component disappears for annealing temperatures above 400 °C, at which temperature the hydrogen has been reported to be largely desorbed. The reduction of the first component with annealing follows the same pattern as other implant elements. The magnetic anisotropy exhibits a large anomalous nonlinear increase with dose. The excess over other implantation elements disappears for annealing temperatures above 400 °C. There is no significant change in gyromagnetic ratio with dose or annealing temperatures up to 600 °C

Electronic Techniques Applied to Analogue Methods of Computation

This paper describes in detail the electronic devices and principles that have been developed for the California Institute of Technology (CIT) electric analogue computer. This is a general-purpose, large-scale computer applicable to a wide range of linear and nonlinear ordinary algebraic or differential equations and linear and nonlinear partial differential equations. In addition to the basic principles of the computer, a detailed discussion is given of those elements considered to be of particular interest. These include the devices for generating the arbitrary functions of the independent variable (the excitation functions), the amplifiers for producing active linear elements such as negative impedances and for representing the nonsymmetrical terms of the matrix specifying the differential equations, the multipliers for producing arbitrary functions of the dependent variables (nonlinear elements). Performance data on these devices are presented, together with analogies and solutions of representative types of problems

Application of the California Institute of Technology Electric Analog Computer to Nonlinear Mechanics and Servomechanisms

This paper describes the non-linear elements and circuit techniques used with the California Institute of Technology electric analog computer. Their application to nonlinear mechanical vibratory systems and nonlinear servomotors is discussed in detail. These techniques have been found to be generally suitable for representing single valued nonlinear functions of a dependent variable. Nonlinear springs, spring loaded backlash, and nonlinear damping factors can be readily simulated as well as saturation effects and other single valued non-linearities in servomotors. Methods of analysis are illustrated for several typical problems including a nonlinear rotating mechanical system and an autopilot employing a solenoid-operated rate and position limited hydraulic motor. Numerous servos of this type have now been studied and correlation of computer solutions with actual servo test data have shown in every case that the mathematical equations presented here accurately describe this type of motor

X-ray rocking curve and ferromagnetic resonance investigations of ion-implanted magnetic garnet

Detailed analyses of x-ray rocking curves and ferromagnetic resonance spectra were used to characterize properties of -oriented Gd, Tm, Ga:YIG films implanted with Ne+, He+, and H + 2. For each implanted species the range of doses begins with easily analyzed effects and ends with paramagnetism or amorphousness. Ion energies were chosen to produce implanted layer thicknesses of 3000 to 6000 Å. Profiles of normal strain, lateral strain, and damage were obtained. The normal strain increases with dose and near amorphousness is 2.5%, 3.4%, and 3.9% for Ne+, He+, and H + 2, respectively. Lateral strain is 0 for all values of normal strain, implying absence of plastic flow. Comparison of these results with the reported decrease in lateral stress implies either a large reduction in Young's modulus or a transition to rhombohedral equilibrium unit cell. Damage is modelled by a spherically-symmetric Gaussian distribution of incoherent atomic displacements. Due to the use of (444), (888), and (880) reflections the sensitivity is greatest for the c sites occupied by Gd, Tm, and Y. The standard deviation of displacements increases linearly with strain with proportionality constant 0.25, 0.18, and 0.13 Å/% for Ne+, He+, and H + 2, respectively. For maximum strains up to 1.3% annealing in air reduces the strain without changing the shape of the profile. The behavior of the strain with annealing is nearly independent of implanted species or doses. After annealing at 600 °C the strain is 40% of the original value. Magnetic profiles obtained before and after annealing were compared with the strain profiles. The local change in anisotropy field DeltaHk with increasing strain shows an initially linear rise for both He+ and Ne+. The slope is −4.1 kOe/%, in agreement with the magnetostriction effect estimated from the composition. For strain values between 1 and 1.5%, DeltaHk saturates reaching peak values of −3.6 kOe for He+ and −2.8 kOe for Ne+. At strain values near 2.3% for He+ and 1.8% for Ne+, DeltaHk drops to nearly 0 and the material is paramagnetic. For peak strains greater than 1.3% for He+ and 1.1% for Ne+ the relation between uniaxial anisotropy and strain is not unique. The saturation magnetization 4piM, the ratio of exchange stiffness to magnetization (A/M) and the cubic anisotropy H1 decrease with strain reaching 0 at 2.3% and 1.8% for He+ and Ne+, respectively. At these strain values the damping coefficient alpha is 50% and 80% greater than bulk value for He+ and Ne+, respectively. For higher observed strains the material remains paramagnetic. Upon annealing of samples implanted with low doses of Ne+ and He+ the anisotropy field follows uniquely the behavior with strain for unannealed material. At 600 °C the magnetization returns to bulk value but the ratio A/M remains 20% low. For H + 2 implantation the total DeltaHk consists of a magnetostrictive contribution due to strain and of a comparable excess contribution associated with the local concentration of hydrogen. The profile of excess DeltaHk agrees with calculated LSS range. The presence of hydrogen results in a reduction of 4piM not attributable to strain or damage. For a peak strain of 0.60% and a peak total DeltaHk of −4.5 kOe, the magnetization is only 40% of bulk value. After annealing up to 350 °C the excess DeltaHk diminishes and redistributes itself to the regions neighboring the peak damage. At 400 °C the excess is nearly 0. For higher annealing temperatures the only component of DeltaHk is magnetostrictive. At 600 °C, the magnetization, the ratio A/M, and alpha return to bulk values