A coded magnet has the temperature limits of the material it is printed on. The pattern does not make the material tougher or weaker.
Most catalog Polymagnets are sintered neodymium (NdFeB). Correlated Magnetics Research's neodymium note says NIB magnets generally operate from -138 C to 80 C (-215 F to 176 F). Its FAQ adds that heat is one of two ways to demagnetize them, at roughly 130 F to 200 F over about 45 minutes depending on grade; the other is a strong reverse field, on the order of five times the strength of an NdFeB magnet. Higher-coercivity grades extend the limit.
For wider ranges, CMR points to samarium cobalt (SmCo). It publishes typical properties for its sintered SmCo grades, and a NASA project shows how far that goes: CMR says it worked with NASA from 2020 to 2022 on 0.6 inch thick SmCo Polymagnets for a magnetic coupler, which kept their force and function above 140 C and below -180 C in testing.
Design with margin. Check the grade's demagnetization curve at your maximum temperature and at the working gap, because a magnet in an open circuit loses strength at a lower temperature than one clamped to steel.
WholeMagnetics, 2026-10-04. Polymagnet facts are taken from Correlated Magnetics Research’s public pages, listed below; vendor performance figures are CMR’s own.