Thermostatistical Theory of Nuclear Spin Structure in Solid ^3He

概要

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The nuclear spin structures observed around 1 mK in bcc solid ^<3>He, which have recently been discussed on the basis of multiple exchange model in the molecular field approximation (MFA), are investigated by the next order approximation. In consequence, a more stability of the up up down down (uudd) phase and accordingly a higher temperature of transition from that to the para-magnetic phase, than by MFA, are derived in contrast with the case of pair exchange in the usual electron spin system in solid. The exchange interactions including the multiple ones are examined by comparing with the previous works. The normal anti-ferromagnetic (naf) and the simple cubic antiferromagnetic (scaf) phases are also investigated in the same approximation. The uudd phase is found the most stable below a transition temperature. Some representative sets of values of exchange parameters are examined in the second order approximation and the observed transition temperature of the uudd phase lies between the estimates by MFA and by the second order approximation.
理論物理学刊行会の論文
1987-01-20