180 deg domain formation in ferroelectrics with shorted electrodes.
180 degree domain formation in ferroelectric crystals unaffected by presence of shorted electrodes due to surface layer properties differing from bulk
MAGNETIC DOMAIN↗
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On the complex state of the interplanetary medium of 28-29 July 1977
Observations of plasma and magnetic field variations in the near-Earth solar wind are discussed. Both a corotating stream and a driven shock are present. The driver gas seems to be enveloped in the rising speed phase of this stream; this appearance is attributed to a convoluted surface separating the two plasma domains. The magnetic field in the post shock flow (0030-1230 UT of July 29) has a large and geoeffective southward component at times; the energy coupling coefficient reaches approximately 5.4 x 10 to the 19th power ergs/s. In the driver gas (1230 UT of July 29 to 0110 of July 30) the magnetic field is dominantly northward. The density and dynamic pressure decrease by almost two orders of magnitude (100 to 2 cm/3) from just behind the interplanetary shock to approximately 3 hours into the driver gas flow. The dominant magnetic field variation in the driver gas is modeled by a cloud-like structure. Significant plasma parameter variations within the driver gas are attributed to structure in the parent solar mass ejection event and to interplanetary kinematics.
King, J. H.↗
Magnetic and magneto-optical properties and domain structure of Co/Pd multilayers
The domain structure of Co/Pd(1.6/6.3 A)xN multilayers and its relation to the bulk magnetic properties of the samples were studied. The Co/Pd multilayers were deposited by rf and dc magnetron sputtering onto different substrates. It was found that magnetic and magnetooptical properties and domain structure of the multilayers were affected by total film thickness and substrate condition. Magnetization, coercivity, and anisotropy of the films decreased significantly as the film thickness dropped below 100 A. However, Kerr rotation angle had a maximum at the same thickness. The width of the domain structure increased with the decrease of the film thickness attaining the single domain state at N = 10. The initial curves in Co/Pd multilayers were found to depend on demagnetization process. The samples demagnetized by inplane field showed the largest difference between initial curves and the corresponding parts of the loops. Different domain structures were observed in the samples demagnetized by perpendicular and in-plane magnetic fields.
Gadetsky, S.↗
Wall motion by reverse neel walls in thin films.
Normal and reverse neel wall motion in thin films
THIN FILM↗
A manually set magnetic wire counter
Magnetic storage wire counter design principles are given. Magnetic storage wire was coupled with two phase propagational driver in manual set counter shift register. Time delay between magnetic counter domain insertion and corresponding output pulse provides counting functions.
Source record↗
Investigation of single crystal ferrite thin films
Materials suitable for use in magnetic bubble domain memories were developed for aerospace applications. Practical techniques for the preparation of such materials in forms required for fabrication of computer memory devices were considered. The materials studied were epitaxial films of various compositions of the gallium-substituted yttrium gadolinium iron garnet system. The major emphasis was to determine their bubble properties and the conditions necessary for growing uncracked, high quality films.
Mee, J. E.↗
A two-degree Kelvin refrigerator
Open-cycle cryogenic refrigerator maintains temperature as low as 2K for periods up to six months. Designed to cool an infrared detector, refrigerator can be used in cooling Josephson-junction devices, magnetic bubble domains, and superconducting devices.
Stephens, J. B.↗
Theoretical grain-size thresholds and their application to accurate methods for paleointensity determination
Improved values of critical grain-size thresholds for magnetite and Fe have been obtained using a rigorous theoretical approach. The temperature dependence of these thresholds is interesting in that it indicates the existence of certain grains which, when cooled from above their blocking temperature, pass sequentially through the following magnetization states: superparamagnetic to single-domain to nonuniform magnetization. Such grains will yield correct paleointensities by the Wilson (1961) or Shaw (1974) method but not by the well-known method due to Thellier and Thellier (1959).
Banerjee, S. K.↗
A solid state data recorder for spacecraft telemetry applications
A solid state data recorder (SSDR) has been developed which offers a high-reliability alternative to tape recorders in many spacecraft telemetry applications. The storage medium used in this recorder was ferrimagnetic garnet films supporting nonvolatile magnetic bubble domains. The recorder was designed using modular construction consisting of a digital control unit, power supply, and two memory modules. A prototype SSDR has been fabricated which is designed for 100-million bits of storage but was populated with 128 chips for a 13-million bit capacity. Preliminary tests indicate satisfactory operation.
Stermer, R. L., Jr.↗
Occurrence of global-scale emissions on Jupiter - Proposed identification of Jovian dimer H2 emission
Two occasions of exceptionally widespread but distinct emission activity were observed in Jupiter's near-IR K-band spectrum during September and November of 1988. Two different sets of emission features were involved on the two dates of observation. During these occasions, the normally absent emission features extended from the South polar limb to at least the equator, over a large range of longitudes. Meanwhile, Jupiter's auroral H2 and H3(+) emissions remained confined to their usual magnetic polar domains. The global-scale emission features observed during those periods appear to have originated from the H2 dimer, (H2)2, during two different excitation modes. Inverse predissociation may have driven the November event. The September event probably originated deeper within the Jovian atmosphere, where excited H2 is more likely to combine with an unexcited H2 before radiating. Unusual magnetospheric loading probably precipitated these events.
Trafton, L. M.↗
Half-State Readout In Vertical-Bloch-Line Memory
Potentially narrow margins of chirality-based chopping of magnetic stripes avoided. Half-state readout is experimental method of readout in Vertical-Bloch-Line (VBL) memory. Based on differential deflections of magnetic stripe domains in which data bits stored. To give meaning to explanation of half-state readout, see "Vertical-Bloch-Line Memory" (NPO-18467).
Katti, Romney R.↗
Passive chevron replicator
There is described a passive replicator device to be used in magnetic bubble domain systems. The replicator is passive, i.e., does not require an active element such as a current source or the like, and both propagates and replicates bubble domains. In a preferred embodiment, the replicator uses chevron type elements arranged in an appropriate pattern so as to interact with a pair of propagation paths wherein bubble domains are propagated. A bubble in one propagation path is routinely transferred therealong and, concurrently, replicated by the instant device into another propagation path. A plurality of elements arranged in juxtaposition to the chevrons assists in controlling the propagation of the bubbles through the respective propagation paths and, at the appropriate time, provides a cutting action wherein a bubble which is elongated between the chevrons of the two propagation paths is split into two separate bubbles.
Oeffinger, Thomas R.↗
Magnetic gradiometry using frequency-domain filtering
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Jodie B Ream↗
Tetrad bubble domain chip arrangement for multiplexing
Rotating magnetic field of bubble domain memory is used to obtain time-division multiplexing of bubble domain circuits into quadrants. Memory bits are assigned on bit-per-chip rather than bit-per-module basis; power is reduced by circulating only portion of bubbles at a time.
Almasi, G. S.↗
Magnetic properties and magnetic hardening mechansim of Pt-Co-B alloys
The intrinsic coercivity is found to be maximized in the Pt42Co45B13 ternary alloy which is undercooled and rapidly solidified (quenched using a 70 m/s wheel speed after undercooling), and then annealed (800 C for 2400 min). The same alloy, processed at slower cooling rates and annealed in the same way, has a much larger scale microstructure and a much lower resulting magnetic coercivity. The microstructure which would optimize the coercitvity of this coercivity of this ternary alloy is a completely ordered L1(sub zero) Pt-Co matrix with a submicron magnetic single-domion Co-boride precipitate. The L1(sub zero) phase is highly anistropic magnetically while the Co-boride precipate is somewhat less so. Annealing treatments designed to produced single-domain Co-boride precipitates enhance the coercivity. This suggests that the refined microstructures is responsible for the high coercivities found in the rapidly solidified and annealed alloy. The magnetic domain wall thickness for a Co-boride precipitate is determined from both experimental observation and theoretical calculation in order to evaluate its influence on the coercivity of the alloy. The effects of the pinning of domain walls and the barrier to the nucleation of reverse domains on the coercivity are discussed. Both microstrucutral analysis and theoretical calculation indicate that the high coercivities in the Pt42Co45B13 alloy are due to the difficult nucleation of reverse magnetic domains.
Qiu, Ning↗
Magnetospheric Multiscale Satellite Observations of Parallel Electron Acceleration in Magnetic Field Reconnection by Fermi Reflection from Time Domain Structures
The same time domain structures (TDS) have been observed on two Magnetospheric Multiscale Satellites near Earth's dayside magnetopause. These TDS, traveling away from the X line along the magnetic field at 4000 km/s, accelerated field-aligned approx. 5 eV electrons to approx. 200 eV by a single Fermi reflection of the electrons by these overtaking barriers. Additionally, the TDS contained both positive and negative potentials, so they were a mixture of electron holes and double layers. They evolve in approx.10 km of space or 7 ms of time and their spatial scale size is 10-20 km, which is much larger than the electron gyroradius (less than1km) or the electron inertial length (4 km at the observation point, less nearer the X line).
Mozer, F. S.↗
Cosmic strings - A problem or a solution?
The most fundamental issue in the theory of cosmic strings is addressed by means of Numerical Simulations: the existence of a scaling solution. The resolution of this question will determine whether cosmic strings can form the basis of an attractive theory of galaxy formation or prove to be a cosmological disaster like magnetic monopoles or domain walls. After a brief discussion of our numerical technique, results are presented which, though still preliminary, offer the best support to date of this scaling hypothesis.
Bennett, David P.↗
Comparison of two methods of performing the Thellier experiment
Two methods for performing the Thellier experiment on paleointensity determinations are compared. The first method is essentially that of Coe (1967) and the second is a slight modification of it. Prepared samples containing different species of magnetic particles are used, and both methods are always performed on the same sample. The study is designed to accent procedural differences between the two methods. It is shown that only the Coe method yields linear PNRM-PTRM (Partial ThermoRemanent Magnetization) plots for single domain and pseudo-single domain particles, because it maintains the symmetry between high-temperature VRM (Viscous Remanent Magnetization) and spontaneous decay, whereas for the modified Coe method the spontaneous decay is enhanced. For multidomain remanence, even the Coe method yields a nonlinear concave-up PNRM-PTRM plot. Paleointensity determinations employing only the ratio NRM/TRM provide no means of evaluating the reliability of the results.
Levi, S.↗