Repair MRAM that's been exposed to a magnetic field
You don't want to remove the magnetization by degaussing. Typically, the magnetic tunneling junction (MTJ) in an MRAM cell has one ferromagnetic layer whose magnetization can be changed by applying a current and one ferromagnetic layer that is pinned, meaning that its magnetization does not change.
I suppose that if you exposed the MRAM to a very high magnetic field you could change the magnetization of the pinned layer so that the MTJ didn't work properly. If that's the case then you might be able to fix it by applying the desired magnetic field to the pinned layer, but that sounds risky to me and you would need to consult the MRAM manufacturer.