New York CNN — General Motors has entered into a partnership with a small Wisconsin start-up, Niron Magnetics, to develop electric motor magnets that can be made without rare elements that are mostly sourced from China today. In electric vehicle motors, rapidly shifting magnetic fields spin a rotor made with magnets that contain “rare Earth minerals” such as terbium and dysprosium. China accounts for a large percentage of the world’s rare Earth minerals supply, according to the United States Geological Survey. And among those minerals used for EV motor magnets, China is responsible for about 90%, according to Niron. Niron…