Scanning SQUID Platform selected customer applications
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Microscopy
Solutions
A scanning-SQUID microscope is an ultra-sensitive system for quantitative measurement of weak local magnetic fields on the microscale . The probe consists of a superconducting quantum interference device ( SQUID ), which is scanned several hundreds of nanometers above the sample surface .
The biggest advantage of sSQUIDs over other magnetic scanning probe techniques is its unmatched magnetic field sensitivity down to the nT range [ 1 ]. The drawback on the other hand is the limited spatial resolution of usually above 1 µ m only , although there are some promising new approaches with much higher spatial resolution [ 2 ].
Collaborating with the group of K . Moler & J . Kirtley ( Stanford , USA ), attocube has designed a platform for cryogenic sSQUID , based on the attoSHPM . The microscope includes all necessary scanner , positioners , cabling , electronics and a sensor head with an adjustable tilt stage for the sensor , but no SQUID sensor or SQUID electronics . It provides a low temperature lateral scan range of 125 μm , which can optionally be equipped with encoders for closed loop operation and fully linearized scans .
If needed , a specially adapted microscope configuration allows for large temperature gradients of up to 100 K ( liquid cryostat ) between SQUID sensor ( kept at less than 7 K ) and the sample [ 3 ].
This allows to study temperature dependent effects and samples with high transition temperatures despite using a sensitive superconducting device .
50 µ m
Internal magnetic fields in natural sands
In this application , samples of natural sand were investigated with a cryogenic sSQUID as described above . The measurements indicate large internal magnetic field variations over tens of microns with up to 2 mT , as well as variations in excess of 50 µ T over smaller ranges . These findings clearly show that unaccounted internal fields can significantly alter NMR data in unknown samples [ 4 ].
[ 1 ] M . Zech et al ., Microscopy Today 19 ( 06 ), 34-38 ( 2011 ) [ 2 ] A . Finkler et al ., Rev . Sci . Inst . 83 , 073702 ( 2012 ) [ 3 ] B . Kalisky et al ., Nature Materials 12 , 1091 ( 2013 ) [ 4 ] J . O . Walbrecker , B . Kalisky , D . Grombacher , J . Kirtley , K . A . Moler and R . Knight , Journal of Magnetic Resonance 242 , 10 – 17 ( 2014 ) attoMICROSCOPY
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