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 respect 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 ferromagnetism at a finite external magnetic field, which leads to a threefold jump in the magnetization as was observed by the experiment. Thus, this state is a strong candidate for the nuclear magnetic ordering in scandium below T ≲ 2[μK].