- 作者: 任盛源
- 作者服務機構: 中央研究院物理研究所
- 中文摘要: 在任何溫度下,每一磁牆均具有非零值的熵 S*。當這些磁牆順著溫差梯度dT/dx移動時,它們即組成一卡諾引擎,而將熱與熵從熱庫傳至冷庫。並且利用磁牆熵力而作工。從基本的 Onsager 公式,我們可以推導出磁牆熵力 F= -S*dT/dx。該結果與文獻一相符。它說明了藉著磁牆表面張力的測量,我們可以大約的測出磁牆熵推動磁場 H 。其大小約略與所研究材料中的頑磁力 H 相當。這就證明當產生磁牆運動時,磁牆熵力亦可能是導動的因素。
- 英文摘要: At any finte temperature, a magnetic domain wall contains a non-zero entropy S*. When this do-main wall moves across a temperature gradient dT/dx, it constitutes a thermal engine carrying entropy andheat from a hot reservoir to a cold reservoir, and transforming it into work through the wall-entropy forceF. From the basic equivalent Onsager equation, we derive the result F = -S*dT/dx, which agrees with thatpredicted in Ref. 1. A rough estimate of wall-entropy drive field H is made through the measurement ofthe wall surface energy. The order of magnitude of H is comparable to the bulk pinning force H of thematerial studied. This indicates that wall-entropy mechanism is also active in driving walls into TDDmotions.
- 中文關鍵字: domain; entropy; surface energy
- 英文關鍵字: --