摘要:

The possible spectroscopic consequences of unequal distribution of the RE3+ions on the six nominally equivalent Y3+sites of garnet are described. The crystal material is in the general case biaxial rather than cubic, and we derive expressions for the absorption coefficient as a function of polarization and growth direction. For non‐Kramers RE3+ions the transitions are x, y or z polarized and the dichroism of the ion can be used to quantitatively determine the distribution on the sites, and to partially determine the symmetry of the crystal field states. The effect of site selectivity on the electronic Raman spectrum is also discussed. Components of the Raman tensor not readily accessible by other means can be measured.

ISSN:0094-243X    

DOI:10.1063/1.3699421

出版商:AIP    

年代:1972

数据来源: AIP

摘要:

Using ferromagnetic resonance techniques, we have measured the growth‐induced uniaxial magnetic anisotropy, Ku, vs. T, of epitaxial garnet films of composition Er2EuGa0.7A10.7Fe3.6012from 98°K to the Curie point, 370°K. The films were grown by liquid phase epitaxy on {111} substrates of Gd3Ga5012. At 300°K they supported bubbles ∼5&mgr;m in diameter with mobilities of ∼320 cm/sec Oe. An unusual combination of properties of these films, i.e., the reasonably narrow resonance line widths, the large g‐factors (∼5), the suitable values of Kuand K1, and the uniaxiality arising from the {111} substrate orientation made observation of both the transverse and longitudinal resonances possible at 17.5 GHz over this entire temperature range, and thus enabled quantitative measurements of Ku(T) to be obtained for the first time. Kuwas found to vary as (Tc−T)1.15 from 98°K to 350°K. At 300°K, Kuis 1.33×104erg/cm3. Attempts can now be made to correlate quantitatively Ku(T) with theoretical studies. The temperature dependence of 2Ku/M, 4&pgr;M, g‐factor, and K1(including small strain terms) have also been measured. An interesting new feature of the uniaxial field, 2Ku/M, is a reversal in slope with a maximum at 185°K. This indicates that below 185°K, M increases faster than Ku. This does not occur at any T⪞20°K for the cubic term, K1/M, of any known mixed or single rare earth iron garnet.

ISSN:0094-243X    

DOI:10.1063/1.3699422

出版商:AIP    

年代:1972

数据来源: AIP

摘要:

The effect of site selectivity on the dipolar and crystal field energy of a mixed rare‐earth iron garnet is calculated. The calculated uniaxial part of the growth‐induced anisotropy of Y2Gd Fe4.2A10.8012is in good agreement with experiment from 4.2 to 300 K. Some other mechanism is necessary to account for the rhombic part.

ISSN:0094-243X    

DOI:10.1063/1.3699423

出版商:AIP    

年代:1972

数据来源: AIP

摘要:

Magnetic bubble circuits which use bubble‐bubble interactions, such as a telephone line scanner, a bubble crossover, and data transfer gates are described. The design of these circuits has been aided by theoretical studies of bubble‐bubble interactions.

ISSN:0094-243X    

DOI:10.1063/1.3699424

出版商:AIP    

年代:1972

数据来源: AIP

摘要:

Electron beam technology (EBT) has been used to fabricate an operational 400‐bit shift register with a density of 3×106bits/in2. This shift register was fabricated on a garnet epitaxial film supporting 4&mgr;m bubbles. EBT should be readily extendable to fabricate bubble devices with a density of 107bits/in2. This is demonstrated by fabrication of permalloy overlay patterns with a line width of 0.3&mgr;m (3000A˚) and a resulting density of 108bits/in2. Details of the fabrication process and the operational characteristics of the register are presented.

ISSN:0094-243X    

DOI:10.1063/1.3699425

出版商:AIP    

年代:1972

数据来源: AIP

摘要:

This paper describes the fabrication and operation of a 52‐bit bubble domain memory chip designed to test the concept of on‐chip magnetic decoding. Access to one of the chip's four shift registers for the read, write, and clear functions is by means of bubble domain decoders utilizing the interaction between a conductor line and a bubble. All other functions are performed by a permalloy overlay driven by an external rotating field. The metallurgy consists of 200 A˚ evaporated permalloy for magnetoresistive sensors. 4000 A˚ electroplated permalloy for propagation etc., and 6000 A˚ electroplated copper for control lines.

ISSN:0094-243X    

DOI:10.1063/1.3699426

出版商:AIP    

年代:1972

数据来源: AIP

摘要:

This paper describes the conceptual design of a highly reliable 108‐Bit Bubble Domain Memory for the Space Program. The Memory has random access to blocks of closed‐loop shift registers, and utilizes self‐contained bubble domain chips with on‐chip decoding. Tradeoff studies show that the highest reliability and lowest power dissipation is obtained when the memory is organized on a bit‐per‐chip basis. The final design, has 800 bits/register, 128 registers/chip, 16 chips/plane, and 112 planes, of which only seven are activated at a time. A word has 64 data bits +32 checkbits, used in a “16‐adjacent” code to provide correction of any combination of errors in one plane. 100 KHz maximum rotational frequency keeps power low (≤ 25 watts) and also allows asynchronous operation. Data rate is 6.4 megabits/sec, access time is 200 &mgr;sec to an 800‐word block and an additional 4 msec (average) to a word.

ISSN:0094-243X    

DOI:10.1063/1.3699427

出版商:AIP    

年代:1972

数据来源: AIP

摘要:

An attempt was made to use an InSb Hall‐effect transducer to detect magnetic bubble domains. An InSb film of 1.4&mgr; thickness was evaporated on a glass substrate and then photoetched to cross shape. The width of each branch was 50&mgr;. The product sensitivity of the detector in a uniform field was 220V/AT for a low input current (< 1 mA) and 110V/AT for a high current (7mA). By using this detector a maximum signal voltage of 8mV was obtained at an input current of 7mA for 100&mgr; bubble domains of TmFe03. At 2Hz operation, S/N was quite large (26dB). Noise voltage becomes higher with increasing frequency. This is induction noise in the lead wires by the rotating field. The value of S/N was 10dB at a 38kHz operation.

ISSN:0094-243X    

DOI:10.1063/1.3699428

出版商:AIP    

年代:1972

数据来源: AIP

摘要:

Magnetic bubble domains in both bulk‐grown and epitaxially‐grown magnetic garnets have been detected at frequencies up to 110 kHz using permalloy magnetoresistance elements. The sensors were connected in a bridge configuration to cancel the response of the individual sensors in the absence of a bubble domain. The detector was placed on the side of the bulk crystal platelet opposite the bubble propagation channel, and on the same side as the channel for the epitaxial material. The 10‐&mgr;n diameter bubbles in the bulk crystal delivered 1000‐&mgr;V outputs at a S/N ratio of 14 dB and the 5‐&mgr;m diameter bubbles in the epitaxial crystal delivered outputs of 175 &mgr;V at a S/N ratio of 13 dB.

ISSN:0094-243X    

DOI:10.1063/1.3699429

出版商:AIP    

年代:1972

数据来源: AIP

摘要:

A method is described for determining the magnetization and intrinsic length of thin magnetic films which support magnetic bubble domains. It is shown that from a calculation of the energy of the stripe domain configuration and Thiele's curves for circular domain collapse conditions, the magnetization and intrinsic length may be determined from the measurements of the film thickness, the domain period, and the bubble collapse field.

ISSN:0094-243X    

DOI:10.1063/1.3699430

出版商:AIP    

年代:1972

数据来源: AIP