Boutis G S, Greenbaum D, Cho H, Cory D G, Ramanathan C
Department of Nuclear Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Phys Rev Lett. 2004 Apr 2;92(13):137201. doi: 10.1103/PhysRevLett.92.137201. Epub 2004 Mar 29.
Reciprocal space measurements of spin diffusion in a single crystal of calcium fluoride (CaF2) have been extended to dipolar ordered states. The experimental results for the component of the spin diffusion rate parallel to the external field are D(parallel)(D)=29+/-3x10(-12) cm(2)/s for the [001] direction and D(parallel)(D)=33+/-4x10(-12) cm(2)/s for the [111] direction. The measured diffusion rates for dipolar order are faster than those for Zeeman order and are considerably faster than predicted by simple theoretical models. It is suggested that constructive interference in the transport of the two-spin states is responsible for this enhancement. As expected, the anisotropy in the diffusion rates is observed to be significantly less for dipolar order compared to the Zeeman case.
在氟化钙（CaF₂）单晶中，自旋扩散的倒易空间测量已扩展到偶极有序态。平行于外场的自旋扩散率分量的实验结果为：对于[001]方向，D(平行)(D)=29±3×10⁻¹² cm²/s；对于[111]方向，D(平行)(D)=33±4×10⁻¹² cm²/s。测量得到的偶极有序态的扩散率比塞曼有序态的扩散率更快，且比简单理论模型预测的要快得多。有人认为，双自旋态传输中的相长干涉是这种增强的原因。正如预期的那样，与塞曼情况相比，偶极有序态下扩散率的各向异性明显更小。
