Production and Observation of a Nuclear Antiferromagnetic State
Production and Observation of a Nuclear Antiferromagnetic State
复制标题
核反铁磁态的产生和观测
DOI：
10.1063/1.1658984
复制
发表时间：
1970
影响因子：
3.2
通讯作者：
A. Abragam
中科院分区：
文献类型：
--
作者：
M. Chapellier;M. Goldman;Vu Hoang Chau;A. Abragam
在大多数抗磁性物质中，核自旋之间的偶极相互作用的强度是这样的，以至于必须获得微度或更低的温度才能发生合作效应。我们没有冷却整个样品，而是直接冷却了CaF 2中19 F的核自旋，由于自旋-晶格弛豫机制的弱点，这些核自旋在实验期间被热隔离。冷却分两步进行。首先，自旋在高磁场中通过“固体效应”极化到5毫摄氏度的等效温度。第二，它们在旋转框架中被去磁，达到低于1微度的温度。对于负温度，它们的横向磁化率作为初始极化的函数表现出反铁磁行为的平台特征。结果与分子场理论定性一致。
In most diamagnetic substances the strength of dipolar interactions between nuclear spins is such that temperatures of the order of a microdegree or less must be obtained for cooperative effects to take place. Rather than cooling the whole sample we have cooled directly the nuclear spins of 19F in CaF2, which are thermally isolated for the duration of the experiment by the weakness of the spin‐lattice relaxation mechanism. The cooling takes place in two steps. First, the spins are polarized in a high field by the ``solid effect'' to an equivalent temperature of the order of 5 mdeg. Second, they are demagnetized in the rotating frame reaching a temperature below one microdegree. For negative temperatures their transverse susceptibility as a function of initial polarization exhibits a plateau characteristic of antiferromagnetic behavior. Results are in qualitative agreement with a molecular field theory.