Nuclear dipolar magnetic ordering

Abstract

This article reviews the subject of magnetic ordering in nuclear spin systems subjected to dipole-dipole interactions. This study has been developed so far in only one laboratory, the laboratory of Nuclear Magnetism at Saclay. The impetus was given by Professor A. Abragam, who invented a method for producing the very low temperatures necessary for achieving nuclear magnetic ordering [1, 2]. The first experimental investigation, by M. Chapellier, Vu Hoang Chau and the author, was directed at producing antiferromagnetism in calcium fluoride. Later were involved J.F. Jacquinot, working on calcium fluoride, S.F.J. Cox - a three-year visitor - and V. Bouffard, who looked for antiferromagnetism in lithium fluoride, W.Th. Wenckebach who during a one-year visit contributed to the study of ferromagnetism in CaF 2 and to that of antiferromagnetism in LiF, and Y. Roinel who works with V. Bouffard on lithium hydride. Two technicians, J. Vaissière and C. Pasquette, contribute to the experimental work. The study of nuclear magnetic ordering is still under progress, and many of the expected phenomena still await experimental verification. The decision as to what is the proper time to write a review article is then by necessity largely arbitrary. This article will essentially consist of two parts: a description of the principles and of the theoretical approximations used to study nuclear magnetic ordering, followed by a description of the experimental investigation already completed or under way. No attempt has been made to give detailed credit to every one for his particular contribution, since everybody has been involved in the building and clarification of the physical concepts and experimental ideas through innumerable discussions.