A new magnetic spin device can be used as a memory element or logic gate, such as an OR, AND, NOT, NOR and NAND gate. The state of the magnetic spin device is set inductively. A magnetic spin transistor/gate can be operated with current gain. Furthermore, inductive coupling permits the linking of multiple spin transistors and spin transistor gates to perform combinational tasks. A half adder embodiment is specifically described, and other logic gates and combinations of half adders can be constructed to perform arithmetic functions as part of a microprocessor.