Macroscopic Quantum Tunneling of Magnetic Domain Wall in Ferromagnetic Composite Thin Films

这种调查的目的是为了澄清量子隧道的磁域墙，将其插入到复合薄膜中的硬铁磁、软铁磁和超导体组成中的钉中心。本研究由三个部分组成：（1）在复合导线上有一个别针中心的磁化逆转过程， （2）在复合薄膜上有磁性逆转过程，以及（3）在非常薄的铁导线上有银河效应。这些结果按以下顺序汇总。（1）具有亚微米Fe-Ni线的三层结构的磁化反向过程和墙置换速度通过测量电阻力进行了调查。据估计，隔离墙的流动性约为2.6米/秒，应考虑到吉尔伯特转储过程。（2） The magnetostatic interaction dominates the magnetization process of hybrid films consisting of ferromagnetic Fe and superconducting Nb. Fe电影中的域结构可能取决于任何Nb是超导电还是不导电，这将影响磁性反向。（3） The conductance of the nanowire produced by a tip and contact method was quantized in the unit of 2 eイD12イエD1/h below 67 Oe and eイD12イエD1/h above 67 Oe. The spin degeneracy plays an important role in the conductance quantization。不幸的是，量子宏观隧道的存在很难在最少的阶段确认。

The purpose of this investigation is to clarify the quantum tunneling of magnetic domain wall into the pinning center in the composite thin film consisting of hard ferromagnet , soft ferromagnet and superconductors. This study is composed of three parts ; (1) the magnetization reversal process in ferromagnetic composite wire having a pinning center, (2) the magnetization reversal process in composite thin films, and (3) the galvanomagnetic effect in very thin ferromagnetic wire. The results are summarized as follows. (1) The magnetization reversal process and the wall displacement velocity in submicron Fe-Ni wire with tri-layer structure were investigated by measuring the electric resistance. The wall mobility was estimated to be about 2.6 m/sOe, due to Gilbert damping process. (2) The magnetostatic interaction dominates the magnetization process of hybrid films consisting of ferromagnetic Fe and superconducting Nb. The domain structure in the Fe film may depend on whether Nb is superconducting or not, and this affects the magnetization reversal. (3) The conductance of the nanowire produced by a tip and contact method was quantized in the unit of 2eィイD12ィエD1/h below 67 Oe and eィイD12ィエD1/h above 67 Oe. The spin degeneracy plays an important role in the conductance quantization. Unfortunately, the existence of the quantum macroscopic tunneling was hard to confirm at least present stage.