What kind of glue can be used for mounting the samples in SQUID magnetometer to work above 400 K and giving minimal or marginally small magnetic signal?
PVA is good. but it is up to 70 C. Silicon rubber can bear high temperature but as I know, they have small signal (you may can abstract it). In my tests I pressed powder samples in some kind of capsule manually (no high pressure is used as a bellete).
I admittedly don't know anything about the magnetic signal or what material you are bonding, but I have used a high temperature epoxy resin EL315 that will handle that temperature. See attachment.
You can use Zircar cement ( ACA5) for high temperature application in SQUID. The cement is water soluble and can be removed easily. You can get more details from the application note of QD on VSM sample mounting. (https://www.qdusa.com/sitedocs/appNotes/ppms/1096-306.pdf). Hope it will help.
Indeed, Chandan Upadhyay is right, zircar is a good idea. We keep using it for high temp. measurements as well as for low temp. ones. In pavillion X they should have it, or contact me, I can offer you some zircar to try it out.