I don't think so. While it is true that Thor's hammer was forged with Iron, the hammer itself is imbued with godly magic. Even if Magneto could lift it, I think Mjolnir would reject him and be able to fight off his influence.
Thor's hammer is made of an mythical metal not known to earth and is made of different qualities than our metal and meatal that magneto controls. in a issue I read Thor threw his hammer at magneto and magneto was unable to stop the hammer from hitting him therefore I believe magneto cannot lift Thor's hammer with his powers