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

铁磁复合薄膜中磁畴壁的宏观量子隧道

基本信息

批准号：
09640448
负责人：
MIYAJIMA Hideki
金额：
$ 2.5万
依托单位：
KEIO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09640448/
关键词：
Composite Film Quantum Tunneling Effect Magnetic Domain Wall Pinning Center Ferromagnetic Wire Quantum Wire Galvanomagnetic Effect 量子トンネル効果電気伝導の量子化巨大磁気抵抗効果

项目摘要

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.

本研究的目的是阐明由硬铁磁体、软铁磁体和超导体组成的复合薄膜中磁畴壁进入钉扎中心的量子隧穿。本研究包括三个部分：（1）具有钉扎中心的铁磁复合线的磁化反转过程，（2）复合薄膜的磁化反转过程，（3）极细铁磁线的电流磁效应。结果总结如下。(1)通过测量电阻，研究了亚微米三层结构Fe-Ni丝的磁化反转过程和壁面位移速度。由于吉尔伯特阻尼过程，壁面迁移率估计约为2.6 m/sOe。(2)静磁相互作用主导了铁磁Fe和超导Nb混合膜的磁化过程。Fe膜中的畴结构可能取决于Nb是否超导，并且这影响磁化反转。(3)用针尖接触法制备的纳米线的电导在67 Oe以下量子化为2 e Ω D12 Ω D1/h，在67 Oe以上量子化为2 e Ω D12 Ω D1/h，自旋简并度在电导量子化中起重要作用.然而，量子宏观隧穿的存在至少在现阶段还很难得到证实。