Magnetism of Solid Helium-3

固体氦-3核磁中的几个问题将在低至20微开尔文的温度和高达20特斯拉的磁场下进行研究。在高压六边形封闭堆积相中，由于三重交换的优势，预计将是铁磁性的，将通过使用氦核进行第二阶段的退磁来实现。通过测量熔化压力来获得磁化强度，研究在20特斯拉附近发生的系统完全磁化的高场向顺磁相变。在靠近三相点（低场、高场和顺磁相共存的地方）的低场中这种转变的性质将通过核磁共振和热输运测量来研究。这三项研究将为这种模型磁性物质的基本行为提供额外的见解。固体氦-3被认为是研究磁学基本原理的一个模型磁系。由于质量小，原子间作用力弱，兴趣效应发生在接近绝对零度的温度范围内，低于电子系统的兴趣范围，但高于重核磁体的兴趣范围。由于氦气具有高度可压缩性，因此可以通过施加中等压力来研究在很大密度范围内的效应。特别是，可以研究两种不同类型晶体中的磁性结构类型。研究方法包括核磁共振、熔融压力、等体积压力和导热性。所获得的知识将有助于理解更复杂的磁系统中的磁现象。＊＊＊

9421034 Adams Several problems in nuclear magnetism of solid helium-3 will be investigated at temperatures as low as 20 microkelvin and magnetic fields up to 20 Tesla. Ordering in the high-pressure hexagonal-closed packed phase, which is expected to be ferromagnetic because of the dominance of triple exchange, will be achieved by using the helium nuclei for the second stage demagnetization. The high field to paramagnetic phase transition, which occurs near 20 Tesla where the system becomes fully magnetized, will be studied by measurement of the melting pressure to obtain the magnetization. The nature of this transition at low fields near the triple point ( where the low-field, high-field, and paramagnetic phases coexist) will be investigated by nuclear magnetic resonance and thermal transport measurements. These three investigations will provide additional insight into the fundamental behavior of this model magnetic substance. %%% Solid helium-3 is considered a model magnetic system for studying fundamentals of magnetism. Because of the small mass and weak forces between atoms, the effect of interest occur in a range of temperature near absolute zero, below that of interest for electronic systems, but above those for heavy nuclear magnets. Since the helium is highly compressible, effects can be investigated over a wide range of density by application of moderate pressure. In particular, the type of magnetic structures occurring in two different type of crystals can be studied. Methods of investigation include nuclear magnetic resonance, melting pressure, constant-volume pressure, and thermal conductivity. Knowledge gained will be of use in understanding magnetic phenomena in more complicated magnetic systems. ***