Spin Wave in Solid ³He

Abstract

Using the spin wave theory a few thermodynamic quantities of solid 3 He in the “uudd” phase are calculated. In the first approximation, in which higher terms than the fourth power of Holstein-Primakoff operators are neglected, the contraction of the spin is not small and the gain of the energy at 0 K due to the zero point motion of spins is comparable to the energy associated with the molecular field approximation. If only j t and K P are not zero, this approximation does not explain the experimental results. In the second approximation, in which the contribution due to the fourth power terms is taken into account, the “uudd” phase becomes stable or metastable because of large zero point motion of spins even when J 2 - K F <0, and the exchanges that only j t and K P are not zero, can explain the experimental results, where j t , K P and K F are the triple, planar and folded type cyclic four spin exchanges.