No. Magnetic strips are resistant to 3 tesla, but it does kill them. I assume moving fast across flux lines does it. However chips on the card are good with unlimited exposure to 4.7 tesla as far as I can tell. Phones turn off and won't reboot for a period of time that is alarming, but so far I haven't seen it kill one. MRI engineers even have instructions to document some scanner work with their iPhones. It may just be the screen turning off so I'll have to test Siri or something to check if it's that. They always work again so far but the 30 minute wait didn't seem good!

Many phones have magnetic switches for use with smart cases. When you close the case cover, a small magnet trips the switch and turns the screen off.

The magnet isn't damaging the phone — at least not at field strengths likely to be encountered in everyday life. Removing the magnetic field should immediately turn the screen back on.

4.7t is pretty strong. It isn't a cover detector as it's mainly iPhones I've seen affected and it lasts long after the phone is removed from the field. However this may be what has caused the effect on some of the other phones I've seen exposed. I'll do some experimenting next time it occurs. GE and Seimens seem to have an array of phones that engineers are equipped with and they are happy to expose them to high fields.