螺旋磁性
外觀
螺旋磁性是一種相鄰磁矩的自旋以螺旋模式進行排列的磁序形式,其特徵轉角介於0到180度之間。這種現象是鐵磁和反鐵磁交換相互作用之間競爭的結果,也可以分別將鐵磁和反鐵磁視為具有0度和180度特徵轉角的螺旋磁結構。螺旋磁序本質上可以是左旋或右旋的,因此螺旋磁序破壞了空間反演對稱性。
嚴格來說,螺旋磁體並沒有永久磁矩,因此有時被認為是一種複雜的反鐵磁體。而錐形磁性除了具有螺旋調製外還有永久磁矩(例如,金屬鈥在低於20K時表現出錐形磁性[1])。是否具有永久磁矩可以將螺旋磁體與錐形磁體區分開來。
螺旋磁性的概念於1959年首次提出,它可以作為對二氧化錳磁結構的解釋[2]。螺旋磁性最初應用於中子衍射,後來發現它可以被洛倫茲電子顯微鏡更直接地觀察到[3]。據報道,大部分材料在低溫下表現出螺旋磁性,然而也有一些螺旋磁結構可以在室溫下保持穩定[4]。許多螺旋磁體具有手性立方結構,例如B20晶體結構類型。
就像普通鐵磁體具有分隔各個磁疇的疇壁一樣,螺旋磁體也有自己的以拓撲電荷為特徵的疇壁。 [5]
材料 | 溫度範圍 |
---|---|
β-MnO2 [2][6] | < 93 K |
FeGe, [4] | < 278 K |
MnGe[7] | < 170 K |
MnSi, [8] | < 29 K |
FexCo1−xSi (0.3 ≤ x ≤ 0.85) [9] [10] | |
Cu2OSeO3[11] | < 58 K |
Tb[12] | 219–231 K |
Dy[13] | 85–179 K |
Ho[14] | 20–132 K |
參見
[編輯]參考文獻
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- ^ 2.0 2.1 Yoshimori, Akio. A New Type of Antiferromagnetic Structure in the Rutile Type Crystal. Journal of the Physical Society of Japan (Physical Society of Japan). 1959, 14 (6): 807–821. Bibcode:1959JPSJ...14..807Y. doi:10.1143/jpsj.14.807.
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- ^ Regulski, M.; Przeniosło, R.; Sosnowska, I.; Hoffmann, J.-U. Incommensurate magnetic structure of β−MnO2. Physical Review B (American Physical Society (APS)). 2003-11-03, 68 (17): 172401. ISSN 0163-1829. doi:10.1103/physrevb.68.172401.
- ^ Martin, N.; Mirebeau, I.; Franz, C.; Chaboussant, G.; Fomicheva, L. N.; Tsvyashchenko, A. V. Partial ordering and phase elasticity in the MnGe short-period helimagnet (PDF). Physical Review B (American Physical Society (APS)). 2019-03-13, 99 (10): 100402(R) [2021-09-26]. Bibcode:2019PhRvB..99j0402M. ISSN 2469-9950. doi:10.1103/physrevb.99.100402. (原始內容存檔 (PDF)於2021-12-30).
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