Magnetic phone case safe?

Hello,

I recently bought an iPhone 11, my second as I have another one I bought some months back. This new one gets quite warm while charging while my older one doesn’t. I was thinking maybe it could have something to do with the magnetic phone case I’m using for the newer one. It’s a wallet case with the inside case, the part that the holds the actual phone, held in place by a magnet which you can then take out of the outer wallet. Are magnetic cases safe for iPhones? Could it be what is causing the phone to get warm while charging?