Removing frozen field from SQUID magnetometer MvsH data

[GPhys05032019]

Hi,

I have measured a sample and realized there is a frozen field that remained in the SQUID magnetometer before the MvsH measurements were taken.

I am fairly new to using the SQUID, I have plotted the data and if I multiply the applied field by a factor of 0.75 the data matches what I expect.

Is this allowed? My thought process was that if there is an initial field while the SQUID is charging, this frozen field will also increase from the charging process, as the applied field does, so rather than it being an offset field, is it a factor change?

Thanks for any help

 

[f95toli]

That sounds a bit fishy.
A "frozen" field (that is, trapped flux) should for a "bare" SQUID just give you a field offset..
Now, you are probably using the SQUID in a feedback loop which makes things a bit more complicated; and I guess it is theoretically possible that the trapped flux would result in the magnetometer becoming less sensitive (i.e. a change by a constant factor). However, I would be very careful about drawing any conclusions from that data.

 

[ZapperZ]

That sounds a bit fishy.

I hope that pun was intended, because it was good! :)

Zz.