Commercial SQUID Research Articles

High Resolution High-Pressure Magnetometer Based on the Ice Bomb Incorporated into Commercial SQUID Measuring System.

Simple high-pressure apparatus of the ice bomb type has been incorporated into commercial SQUID measuring system (Quantum Design MPMS). Such obtained high-resolution high-pressure magnetometer allows a static magnetization of different materials of interest, including the fragile and small single crystal specimens of organic materials, to be measured in a wide range of working temperatures (from 1. 7 to∼250 K), applied fields (from ∼0. 001 Oe up to 70 kOe, if the MPMS7 system is employed) and pressures (from ∼0. 1 to ∼2 kbar).

Pressure dependence of the electronic density of states and Tc in superconducting Rb3C60.

The functional dependence of the superconducting transition temperature {ital T}{sub {ital c}} on the electronic density of states {ital N}({ital E}{sub {ital f}}) was determined for Rb{sub 3}C{sub 60} by measuring the magnetic susceptibility under hydrostatic pressure to {approximately} 1 GPa in a commercial SQUID magnetometer. Both {ital T}{sub {ital c}} and {ital N}({ital E}{sub {ital f}}) decrease under pressure at the rates {minus}31{percent}/GPa and {minus}14.5{percent}/GPa, respectively, but lie above the corresponding values for K{sub 3}C{sub 60} at the same lattice parameter. The present results are consistent with weak-coupling BCS theory with characteristic energy {ital E}{sub char}/{ital k}{sub {ital B}}{approx_equal} 320{endash}810 K. {copyright} {ital 1996 The American Physical Society.}

Occurrence of synergism between phospholipids and prostaglandins in extracts of some tissues of commercial squid

The phospholipid compositions, prostaglandin-like activities, and ratios of prostaglandins of groups of E, F and A in prostaglandin extracts of some organs of two species of commercial squid have been investigated.

A miniature pressure cell for a SQUID magnetometer

A miniature cell for the measurement of DC magnetic moments under pressure up to 0.4 GPa was developed. The cell is suitable for use in a commercial SQUID magnetometer and is introduced into the instrument in the same manner as is a regular sample. The pressure is calibrated using the critical behaviour of lead at cryogenic temperatures. The increase in under pressure for is demonstrated.

Accurate temperature regulation in a commercial SQUID magnetometer during fast cooling

A detailed investigation of the temperature profile of the measuring region in a commercial SQUID magnetometer was performed over the temperature range from approximately 1.75 to 350 K. Temperature measurements employing three thermometers mounted along the sample tube, revealed the development of a significant thermal gradient during fast cooling from high temperatures. Comparison with measurements of the time dependence of the magnetic moment of a Pr2CuO4 single crystal indicated that long waiting times may be required for sample temperature stabilization depending upon which thermometer is actively used as a control sensor in the temperature regulation. Highly improved temperature control during fast cooling is achieved using a continuous temperature sweeping mode and a combination of two thermometers.

Magnetic properties of BaFe12−(x+y)SnxCoyO19 single crystals (abstract)

BaFe12−(x+y)SnxCoyO19 single crystals, with 0≤x≤2 and 0≤y≤2, have been grown from high temperature solution by slow cooling using the TSSG method. Magnetic properties of these single crystals have been investigated using a commercial quantum design SQUID magnetometer in the temperature range 6 to 320 K and with a varying field from −5 to +5 T applied parallel and perpendicular to their c axis. It is found that the replacement of part of the Fe3+ ions by Co2+ and Sn4+ ones reduces the anisotropy as well as the saturation magnetization of the materials. For a small amount of substitution, the magnetization as a function of applied fields, which were oriented in the c axis, exhibits a hysteresis loop indicating that the magnetic domain wall moving was pinned by the imperfections of magnetic structures. When the substitution was increased to x+y=2.5, long distance magnetic coupling was destroyed, and the sample behaved as a magnetic granular material consisting of randomly distributed magnetic clusters.

Long-time temperature drift in a commercial SQUID magnetometer

Temperature-calibration measurements using a Pt thermometer placed into a commercial SQUID magnetometer (Quantum Design) instead of the sample have shown a long-time (⩾ 8 h) temperature drift occurring in a SQUID body. It is found, that the amplitude of this drift depends on the measuring set temperature. We present also results of the mixed-state magnetic-moment measurements as a function of time and field performed on Bi 2Sr 2Ca 2Cu 3O 10 high- T c superconductor, which illustrate that the magnetometer temperature drift essentially modifies the true magnetization behavior.

Noise thermometry and 3He melting pressure thermometry

A simple noise thermometer, based on the measurement of the currents produced by the noise voltages over a 44 μω manganin resistor with a commercial SQUID, has been used for temperature measurements between 0.1 K and 0.4 K. Results at the superconductive transition points of AuIn 2, AuAl 2 and Ir (nominally at 208 mK, 162 mK and 100 mK), realized with a NIST SRM 768 device, are consistent with the assigned NIST temperature values within 0.15 percent. 3He melting pressures have been measured at these three points and at the minimum of the melting curve, ( p min=(2.9311 4±0.0002)MPa). Existing data for the melting curve are compared with results of thermodynamic calculations between 2 mK and 250 mK.

Postbreeding Dispersal and Drift-Net Mortality of Endangered Japanese Murrelets

ABSTRACr.-The incidental catch of seabirds in high-seas drift nets was recorded in 19901991 by scientific observers on commercial squid and large-mesh fishery vessels operating in the North Pacific Transitional Zone. Twenty-six Synthliboramphus murrelet deaths were recorded in the months of August through December. All but one were from the Korean squid fishery in a small area bounded by 38?-44?N and 142?-157?E. Five specimens of the dead birds were collected and later identified as Japanese Murrelets (S. wumizusume). As fishing effort was widely distributed over a large area east of Japan, these data suggest that postbreeding Japanese Murrelets migrate north to winter in a relatively small area southeast of Hokkaido, where persistent eddies form at the confluence of the Oyashio and Kuroshio currents. Fronts between cold Oyashio water and Kuroshio warm-core eddies promote the aggregation of zooplankton and pelagic fishes, which in turn may attract murrelets during the nonbreeding season. The estimated total mortality of Japanese Murrelets in high-seas drift-net fisheries represents a significant proportion of the total world population of this rare and endangered species. Received 12 October 1992, accepted 4 April 1993.

Magnetic investigation of rare earth phosphate glasses

Phosphate glasses containing high concentrations of rare earth elements are interesting materials with potentially important applications in laser and optoelectronics technology. In earlier work [1, 2], we used ultrasonic techniques to study the acoustic behaviour of these glasses, which revealed striking variations in their elastic properties. This letter reports on the first magnetic susceptibility and magnetization measurements using portions of the same samples. The samples have the general composition (R203)x(P2Os)l_x, where R = La, Eu, Sm, Nd or Gd. Details of their preparation were given in [3]. We found that a wide range of starting compositions all give a final glass composition near x--0.25, corresponding to the crystalline metaphosphate composition R(PO3)3. The samples weighed between 65 and 290mg, with densities of 3.03.6 g cm -3. Two kinds of magnetic measurements were made using the facilities at the Interdisciplinary Research Centre for Superconductivity at Cambridge. Firstly, a Lake Shore Model 7000 susceptometer was used to measure the ac susceptibility at a field of 3 0 e (240 A m -1) and a frequency of 333 Hz in the temperature range from 2 to 100 K. Checks were carried out to ensure that there were no field or frequency dependencies of the data. On two samples only there were d.c. magnetization measurements at fields up to 10 Oe (800 KAm -1) in the temperature range from 2 to 300 K, which were made using a commercial Quantum SQUID magnetometer in a superconducting magnet. SQUID runs were carried out either at constant field over a range of temperatures, or at constant temperature over a range of fields. In all the measurements the magnetization of the sample container was subtracted from the experimental data. The Nd 3+ and Gd 3+ glasses showed large values of susceptibility with a strong temperature dependence. Several of the samples had an apparent zero offset; that is, the values of susceptibility did not approach zero at high temperatures. This appears to result from an uncorrected experimental artefact, so the curves were shifted by adding or subtracting a constant amount from each measured susceptibility value. Fig. 1 shows susceptibility plotted against the reciprocal temperature for two of the samples. Here

The determination of the supercurrent-phase relation of superconducting weak links in static condition

Two methods are developed for the determination of the supercurrent-phase relation of a weak link over the complete phase range. The weak link is incorporated in a superconducting ring, a so-called SQUID ring, which is constructed in such a way that on either side of the weak link an external supercurrent is inserted. With constant applied magnetic field a circulating supercurrent is induced in the SQUID ring. In the first method an external supercurrent is inserted with such a polarity and size that the difference between the embraced magnetic flux and the applied flux is zeroed. This is accomplished with the help of a commercial flux SQUID detector. The circuit is then balanced; the circulating current is zeroed and the inserted supercurrent flows entirely through the junction. The corresponding phase difference over the junction is determined by the amount of applied flux. In the second method the detected embraced magnetic flux signal is traced as a function of the applied flux in case of zero and finite external supercurrent. It is argued that the two curves which can be obtained in this way can be mapped on each other by a horizontal and a vertical displacement. The horizontal displacement gives the self-inductance of the SQUID ring and the vertical displacement gives the amplification factor so that the complete supercurrent-phase relation can be determined directly. In both methods the self-inductance is less than ( h ̵ 2ei c ) so that flux jumps in the loop do not occur ( i c is the critical current of the weak link). Deviations from a pure sinusoidal supercurrent-phase relation are observed in a s-s'-s Josephson junction.

A low field SQUID magnetometer system for magnetic characterization of high-T c superconducting samples

In this article we describe a simple SQUID magnetometer system useful for the magnetic characterization of high temperature superconductors. The system employs a commercial rf SQUID probe with associated electronics located in a 4He gas exchange cryostat. The system is equipped with a copper coil dc magnet for fields up to 50 Gauss. The cryostat is surrounded by a μ-metal shield that keeps the remanent field to less than 20 mGauss. The apparatus has been used extensively to measure both the superconducting transition temperature and width as well as the relative quantities of magnetic flux expulsion and exclusion. It has therefore served as an important first step in the evaluation of sample quality.

Performance of a 2-hole Y-Ba-Cu-O rf SQUID

A two-hole rf SQUID has been fabricated out of bulk YBCO by drilling two holes and careful erosion of the wall between the holes. Commercial SQUID electronics is inductively coupled to the SQUID through a copper coil glued in one of the holes. Periodic oscillations in V-B characteristic of the SQUID are observed at 77 K. The spectral density of the flux noise in the white noise region is 5·5 × 10−4Φ0 / √Hz. The flux noise is frequency-dependent below 200 Hz.

Occurrence of the cephalopod Martialia hyadesi (Teuthoidea: Ommastrephidae) at the Kerguelen Islands in the Indian Ocean sector of the Southern Ocean

In the Atlantic sector of the Southern Ocean, data from vertebrate predators and commercial fisheries suggests that the distribution of the ommast rephid squid Martialia hyadesi is related to the Antarctic Polar Frontal Zone, but it spreads further to the north in some years (Rodhouse, in press). A mass stranding of M. hyadesi occurred on Macquarie Island in 1971 (O'Sullivan et al. 1983) suggesting that its distribution is c ircumpolar (Rodhouse and Yeatman 1990). However, apart from a single beak collected from the s tomach of a wandering albatross at Mar ion Island (Imber and Berruti 1981) its presence has not, until now, been confirmed in the Indian Ocean sector and in particular it is not included in the list of cephalopods from the Kerguelenian Province (Lu and Mangold 1978). M. hyadesi is a major prey item of the grey-headed albatross, Diomedea chrysostoma, and the southern elephant seal, Mirounoa leonina, at South Georgia (Rodhouse et al. 1990; Rodhouse et al., unpublished data) and is present in the diet o f several other predators in the Scotia Sea area including the wandering albatross, Diomedea exulans (Rodhouse et al. 1987) and the giant petrels, Macronectes halli and M. gioanteus (Hunter 1983). It occasionally occurs as a significant by-catch in the lllex argentinus fishery on the Pa tagonian Shelf and has been taken during commercial squid jigging trials in the Scotia Sea at the Antarctic Polar Frontal Zone (Rodhouse, in press). It appears to have potential for commercial exploitation in the sub-Antarctic waters of the Atlantic sector of the Southern Ocean (Rodhouse 1990). In view of the ecological importance of M. hyadesi to Antarctic predators, and the likelihood that it will be commercially exploited in the future, it is important to thoroughly establish its geographical range, and in particular to confirm its circumpolar distribution.

SQUID magnetometer designed for high Tc superconductors

A SQUID-based magnetometer has been developed for measurement of the magnetization of high T c superconducting materials. The instrument covers the magnetic field range 0–3.5 T and the temperature of the sample can be changed within the range 5–150 K by continuous helium gas flow. Because of the high diamagnetic susceptibility of the samples and to reduce the noise of the instrument, the sensitivity of the system was reduced with a step down flux transformer. A commercial RF SQUID and electronic unit was used as a detector. Some preliminary measurements on samples of the yttrium and bismuth families are presented.

A superconducting six-axis accelerometer

A superconducting device that is capable of measuring acceleration in all six degrees of freedom with great sensitivity is discussed. The device makes use of the fact that a superconducting mass levitated over a set of superconducting coils by a persistent current behaves as if it were supported by spring with a very stable spring constant. The displacement of the levitated mass modulates the inductance of spiral coils in close proximity to it. By forming inductance bridges from sets of such coils and reading the bridge misbalance signal with a SQUID, it is possible to sense very small displacements and rotations of the proof mass. In the first full tests of the device, its scale factor for acceleration (angular acceleration) was found to be approximately 2*10/sup 5/ Phi /sub 0//g (10/sup 3/ Phi /sub 0//rad/s/sup 2/) at the SQUID, in good agreement with values obtained from an analytical model. The inherent acceleration (angular acceleration) noise was found to be approximately 5*10/sup -10/ g/ square root Hz (10/sup -7/ rad/s/sup 2// square root Hz) which corresponds to the expected input noise for the commercial RF SQUID used. A substantial augmentation of the scale factors is possible by increasing the area of the sensing coils and improving the resolution with which the proof mass can be positioned. Such improvements, along with the use of lower noise DC SQUIDs, should allow the inherent acceleration (angular acceleration) noise to be reduced to a value close to the Brownian noise limit, approximately 10/sup -13/ g/ square root Hz (7*10/sup -11/ rad/s/sup 2// square root Hz).

Superconducting kinetic inductance radiometer

A bolometer that is based on a differential thermometer that senses temperature changes through changes in the kinetic inductance of a superconducting thin film is being developed. The temperature transducer is an inductance bridge patterned as an integrated circuit on a 1-cm/sup 2/ Si substrate. Two inductors from opposite arms of the bridge are patterned on a 2-mm/sup 2/ thermally isolated Si island which is supported by a 9- mu m thick Si:B membrane. The bridge is excited with audio-frequency current, and the bridge imbalance is detected with a commercial DC SQUID amplifier. The bridge is balanced by applying power to the thermally isolated island. This thermometer is the sensor for a prototype radiometer that will provide an absolute measure of IR power. The radiometer, which is designed for a NEP of about 10/sup -11/ W/ square root Hz, is intended to measure the spectrally dispersed power of a 300-K black body. This absolute radiometer is being developed for use at the Low Background Infrared (LBIR) Facility at NIST, Gaithersburg, MD. The noise floor of the temperature transducer for the radiometer has been measured to be 0.7 pW for a 100-s integration time. This is approximately 150 times lower noise than that of the commercial absolute radiometer currently used at the LBIR facility.

Fabrication and performance of high T/sub c/ two hole bulk and single hole thick film RF SQUIDs at 77 K

Two-hole YBCO bulk and one-hole YBCO, BSCCO thick-film RF SQUIDs have been fabricated and operated at 77 K. RF SQUID behavior has been studied using commercial RF SQUID electronics with external RF and AF sources. Flux noise density of these SQUIDs depends on the quality of the microbridge. Flux noise present in various reported high-T/sub c/ film RF SQUIDs is compared.

Apparatus for i n s i t u measurement of surface magnetic moments prepared in UHV

An apparatus for making in situ measurements of the magnetic moment of submonolayer through multimonolayer samples deposited in a UHV chamber is described. The UHV chamber is designed to be used with a commercial SQUID magnetometer with a sensitivity of ∼10−8 emu. The component of magnetic moment parallel to the sample surface may be measured over the temperature range 4–400 K and for magnetic fields (applied parallel to the surface) up to 5 T. A thin re-entrant metal tape is used both as an initial substrate for the deposition of any desired films, and as the means of transporting the deposited sample from the evaporation and evaluation regions of the vacuum chamber to the SQUID analysis region. Some results for Fe evaporated on polycrystalline Ag films are presented.

Design and Operation of a Small Tank System for Ovarian Maturation and Spawning of Penaeus vannamei

Ovarian maturation and spawning of Penaeus vannamei was accomplished in a 120 l (30 gal) tank as well as in a 800 l recirculating system consisting of six aquaria plumbed into a common biofilter. Pond reared animals stocked one per tank were fed a diet consisting of commercial pellets, squid, and bloodworms. Temperature was maintained at 28oC and salinity between 28 and 32 ppt. Presence of black shields between aquaria, males, eggs in the water, and other females in the aquaria were not required for ovarian maturation. Thirty-six of 78 females held in the small talk system spawned. The smallest female which spawned was 25.9 g. After unilateral eyestalk ablation by enucleation, female P. vannamei molted in 3-16 days and spawned in 7-20 days. Up to four spawns occurred before the next molt which occurred 15-35 days after ablation.