An 8-T superconducting quantum interference device magnetometer

Abstract

A variable-temperature (1.4–320 K) superconducting quantum interference device magnetometer, operating in magnetic fields up to 8 T, has been built. The sensitivity is 2×10−7 emu in low fields and 2×10−6 in high fields. The apparatus allows magnetization and anisotropy measurements to be performed and is entirely automated. It is of simple construction and has proved over a number of years to be very robust.

Magnetic properties of Th2Fe17Cx compounds (x=,0.6,0.9,1.1)

“…As can be seen from Table II, such reduction of the effective magnetic moment upon increasing the carbon con-TABLE II. Saturation magnetization M s , Curie Weiss constant C, paramagnetic effective moment eff , mean number of spins in the ordered S 0 or paramagnetic states S p and corresponding ratio r = S p / S 0 for the Th 2 Fe 17 C x compounds compared to that of the binary Fe 3 C or ternary ThFe 11 centration has also been observed for the ThFe 11 C x series. A value of 3.89 B per iron atom has been reported for Fe 3 C; 18,19 this is close to the values observed here for the Th 2 Fe 17 C x compounds.…”

Investigation of the pressure and temperature dependence of the intrinsic magnetic properties of YCo4Ge

“…It is worth to mention that the YCo 4 Ge compounds exhibits an anisotropy field significant smaller that what has reported for other YCo 4 X (X¼Al, Si, Ga.) isotypes [20,21,28,35,36]. Indeed these phases present anisotropy field of c.a.…”

“…The same cryostat was used with another insert enabling any temperature between 300 and 850 K to be regulated. This set up has been used to investigate the magnetic properties of the YCo 4 Ge compounds above room temperature and in particular in the paramagnetic region [28]. Following the mean field approach, the Curie temperature was determined from the temperature dependence of the square of the magnetization.…”

Automated and versatile SQUID magnetometer for the measurement of materials properties at millikelvin temperatures

“…As for the maximum applicable magnetic field, although the magnet itself can produce 9 T, the SQUID circuitry tends to become unstable above ∼ 0.2 T. This a rather typical value when no special cautions are taken to stabilize the field and screen the SQUID circuitry from the stray fields: in specialized systems [2,9], operation up to 8 T has been achieved by designing a dedicated magnet with large bore and by adding a NbTi superconducting shield around the sample-and pickup coils-space. We recall that our system is not dedicated uniquely to SQUID magnetometery and can accommodate, for instance, NMR experiments where the possibility of producing continuous field sweeps is essential.…”

“…The really challenging part of the design consists in the fact that, like in most commercial and non-commercial [8,9] magnetometers, to obtain the absolute value of the magnetization we need to move the sample through a gradiometer pick-up coil, but in our case the sample is at T ≥ 10 mK inside the mixing chamber of the dilution refrigerator! The sample movement is needed because the coils of the gradiometer will never perfectly compensate one another, leaving an empty-coil signal that will add a spurious contribution to the measured magnetic moment, or even wash out the signal of the sample to be measured.…”