Monte Carlo study on the nuclear magnetic ordering in scandium crystal: Possibility of a ferrimagnetic state

Nuclear magnetic ordering is investigated in scandium crystal by the Monte Carlo simulation. We determine the phase diagram in the ground state with r espect to interactions between the nuclear spins. In this phase diagram, we find a ferrimagnetic state with the total magnetization being smaller than the complete ferromagnetism by 1/3: This state changes into the ferromagne tism at a finite external magnetic field, which leads to a threefold jump i n the magnetization as was observed by the experiment. Thus, this state is a strong candidate for the nuclear magnetic ordering in scandium below T le ss than or similar to 2[mu K].