SQUID magnetometer

Selected entries from Methods in Enzymology [vol, page(s)] Theoretical aspects, 76, 354-356 diagmagnetic contribution, 76, 358-359 experimental methods, 76, 356-360 Faraday balance technique, 76, 360-361 Gouy technique, 76, 357, 360 instrumentation, 76, 360-369 oxygen contribution, 76, 360, 368 sources of experimental errors, 76, 359-360 SQUID magnetometer use, 76, 364-365 thermal equilibria, 76, 358, 370 thermal expansion, 76, 358. 

The magnetic susceptibilities of dimer liquid crystals such as NC-Ph—Ph—O—(CH2>n—Ph—Ph—CN(n 9, 10) are measured by a SQUID magnetometer. The results obtained are interpreted within the framework of the RIS approximation, the effect arising from the conformational anisotropy of the flexible spacer being strictly taken into account. The order parameters of the mesogenic core axis thus estimated are found to be consistent with those directly observed at just below 7N) by the ZH NMR technique using mesogen-deuterated samples. 

The magnetic susceptibilities of some ether-type liquid-crystalline polymers are measured by a SQUID magnetometer. The Ax values estimated for the stable nematic state are analyzed according to a known RIS scheme. 

FIGURE 3.6 Geometry of pickup coils in second-order gradiometers used in SQUID magnetometers. The sample is moved along the z-axis through the coils. 

There are several factors that have made SQUID magnetometers less attractive than other methods for NQR explosives detection. The SQUID magnetometers used for NQR detection were cooled to 4.2K for operation, as were the flux transformers. SQUIDs are generally broadband devices and must be shielded from stray magnetic fields. Optimal performance is obtained at low frequency, with sensitivity decreasing with increasing frequency. 

Dry powder of the Prussian blue nanoparticles (PB3, 15 nm) was compacted by epoxy glue. The magnetization measurements were performed in a SQUID magnetometer (MPSM - Quantum Design). 

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