Chapter 225 – Rare-earth beta-diketonates

Dynamic hysteresis loop shapes and magnetic power losses are studied in nonoriented Fe-Si laminations exhibiting significant excess losses. Measurements are carried out under controlled sinusoidal induction in the frequency range from 1 Hz to 1.6 kHz, at various peak inductions from 0.25 to 1.5 T. Excess losses are found to obey a f3/2 law up to frequencies of 200–400 Hz, depending on peak induction. Beyond this limit, definite deviations are observed, due to eddy current shielding. Detailed information on the flux and field distribution in this high frequency regime is obtained by finite element solutions of Maxwell equations employing the dynamic Preisach model to describe quasi-static hysteresis and dynamic wall processes. The agreement between theoretical predictions and measurements is discussed.

/pdf/power-losses-in-magnetic-laminations-with-hysteresis-finite-4w3x2wsf9k.pdf

Power losses in magnetic laminations with hysteresis : finite element modeling and experimental validation

MOCVD of superconducting YBa 2 Cu 3 O 7δ thin films using the novel fluorinated barium β-diketonate complex [Ba(TDFND) 2 ·tetraglyme] 1 in combination with [Y(TMHD) 3 ] 2 and [Cu(TMHD) 2 ] is reported. The Ba complex has a low melting point (72°C), is thermally stable to 200°C and allows reproducible and reliable film deposition even when maintained at 145°C for several weeks. Conversion of the fluoride to the oxide is achieved by in situ hydrolysis. Films deposited on SrTiO 3 (100) were characterised by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, rocking curve, ac susceptibility and secondary ion mass spectrometry. Homogeneous layers of YBa 2 Cu 3 O 7−δ , ≈ 0.25 μm thick, were grown at ≈ 0.13 μm h −1 . The films are epitaxial with good c axis orientation. Critical temperatures T c are typically 91 K and critical current densities c (at 77 K) of ≈ 5 MA cm −2 are reported. SIMS results showing levels of residual fluorine do not exceed 250 ppm.

MOCVD of high quality YBa2Cu3O7−δ thin films using a fluorinated barium precursor

Measuring the limpness of a note (10) is necessary to separate a worn note (10a) out of circulation Several methods are disclosed which can be used either alone or in combination to test for limpness One method measures the note's ability to reflect light (12 and 20) or transmit the light (12 and 22) Another method measures the response of the note (10) to an acoustic wave (24, 26, 28 and 30) Another method measures the note's deflection to a pressure of force (32, 34 and 38) Yet another method measures the dielectric value of the note (10) when placed between the plates (38 and 40) of a capacitor A final method involves measuring the thermal conductivity (42 and 44) of the note (10) In each case, a limp note (10a) will produce distinguishable results from a stiff note (10)

Methods of measuring currency limpness

MOCVD of high-TC superconducting materials

Thin‐film growth and compositional effects of c‐axis oriented YBa2Cu3O7−x (YBCO) thin films synthesized by metalorganic chemical vapor deposition have been investigated. The formation of single cation films using tetramethylheptanedionate precursors was shown to be mass controlled, exhibiting a ratio of deposited to evaporated species in the increasing order Ba, Y, and Cu. The physical properties of off‐stoichiometric YBCO films deposited on MgO substrates were measured in the compositional range 1.1≤Ba/Y≤2.3 and 1.5≤Cu/Ba≤4.6. While structural properties such as c‐axis values and rocking curves appeared unaffected to variations in cation stoichiometry, morphology was observed to be extremely sensitive even to slight changes in composition. Off‐stoichiometric layers with Cu/Ba≳1.5 were observed to exhibit Cu‐rich precipitates embedded in a 1:2:3 YBCO film matrix. The zero‐resistivity temperatures were above 77 K for all cation film compositions measured. However, sharp ac‐susceptibility transitions were r...

Thin‐film growth and compositional effects in YBa2Cu3O7−x layers prepared by metalorganic chemical vapor deposition

Growth and properties of MOCVD YBa2Cu3O7−x thin films

The cobalt reactivity on monocrystalline silicon has been studied for annealing temperatures lower than 500 °C. The techniques used were thermomagnetism measurements and transmission electron microscopy. The results demonstate that the reaction starts during deposition. During annealing the three types of formation kinetics were shown to exist as a function of temperature (20–220 °C, 220–370 °C, 370–420 °C). At the latter temperature the cobalt is completely transformed into CoSi and Co2Si.

Magnetic and transmission electron microscopy studies of the formation of cobalt silicide thin films

The critical current density (Jc) for zero magnetic field has been measured as a function of temperature in c-oriented thin layers of YBa2CU3O7-x prepared by different synthesis methods. One direct and two indirect Jc(T) methods were employed for each film: transport measurements on patterned film constrictions, DC remanent magnetization studies using the Bean model and non-linear AC screening analysis. Results from the indirect methods were calibrated against transport data. Possible origins of observed dependences are suggested and calibration procedures are discussed. The investigation demonstrated the feasibility of using AC screening analysis in rapid determinations of Jc(T) close to Tc.

https://iopscience.iop.org/article/10.1088/0953-2048/7/4/003/pdf

Measurements of critical currents as a function of temperature in YBa2Cu3O7-x thin films: a comparative study

For the recognition of special papers for security reasons, a magnetic mark is introduced which can be read or distinguished by the steps of heating the paper, submitting it to a magnetic detector, and heating it further and again submitting it to magnetic detection. The addition of magnetic impulses collected during the two readings provides a parity of impulse frequency which may be detected by sensitive equipment. The method enables selective recognition of paper types or parcels to a very fine degree: it will reject magnetic material other than that previously selected for the machine ot identify, and provides a 'magnetic key' for controlling selection.

Appts. for identifying security paper - has two heaters, and two detectors for magnetic fields

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