Thank you, and you are correct I meant MU-metal.

just a clarification I don't want to heat it. my question is more along the line, can you pas a current through it and disrupt its magnetic shielding property's. like a switch.

I was going to cut slots in it. heating it to 870F might be a viable option, do you know if i can heat parts of it and destroy the ferromagnetic properties in those spots altogether.

If you pass a current through it and the resulting heat is not sufficient to increase the temperature above the curie temp, then it shouldn't change from ferromagnetic to paramagnetic. A new current would lead to magnetic flux in accordance with the right hand rule convention.

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I don't know what would happen to the ferromagnetic properties if you applied high voltage very high frequency AC to Mu-metal thin enough for skin effect not to be a major concern.....I'd be interested if you dig anything up on this.

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The change due to heating is reversible (therefore not 'altogether', in the sense I believe you to be asking) passing through the curie temp.... ferromagnetic to paramagnetic on the way up, reversing back to ferromagnetic on the way back down.