Institut Néel, CNRS and Université Joseph Fourier, BP 166, 38042 Grenoble Cedex 9, France.
Phys Rev Lett. 2012 Dec 7;109(23):237001. doi: 10.1103/PhysRevLett.109.237001. Epub 2012 Dec 3.
We present low field magnetization and susceptibility measurements made on a single crystal of the ferromagnetic superconductor UCoGe. The interplay between ferromagnetism and superconductivity comes into view in the study of hysteresis along the c axis (easy magnetization axis). The Meissner state (perfect diamagnetism) could not be observed in very low magnetic fields for all three crystallographic directions, implying that the sample is always in the mixed state. Notwithstanding, the Meissner-Ochsenfeld effect (reversible flux expulsion) occurs and is found to be anisotropic. For the c axis in low fields, it is proportional to the bulk magnetization M (and thus to the population of domains) and not to the applied magnetic field H. On a microscopic level, our interpretation of these results implies that flux is expelled independently from each domain proportional to its volume.
我们展示了在单晶体 UCoGe 上进行的低场磁化率和磁化强度测量。在沿 c 轴（易磁化轴）的磁滞研究中，可以看到铁磁性和超导性之间的相互作用。在所有三个晶体学方向上，都无法在极低磁场中观察到迈斯纳态（完全抗磁性），这意味着样品始终处于混合态。尽管如此，迈斯纳-奥赫森菲尔德效应（可逆磁通排斥）仍然存在，并且呈现各向异性。在低场中，对于 c 轴，它与体磁化强度 M 成正比（因此与畴的数量成正比），而与外加磁场 H 无关。从微观角度来看，我们对这些结果的解释意味着磁通从每个畴中独立排斥出来，与畴的体积成正比。
