Helimagnetism

Helimagnetism is a form of magnetic ordering where spins of neighbouring magnetic moments arrange themselves in a spiral or helical pattern, with a characteristic turn angle of somewhere between 0 and 180 degrees. It results from the competition between ferromagnetic and antiferromagnetic exchange interactions. It is possible to view ferromagnetism and antiferromagnetism as helimagnetic structures with characteristic turn angles of 0 and 180 degrees respectively. Helimagnetic order breaks spatial inversion symmetry, as it can be either left-handed or right-handed in nature.

Strictly speaking, helimagnets have no permanent magnetic moment, and as such are sometimes considered a complicated type of antiferromagnet. This distinguishes helimagnets from conical magnets, (e.g. Holmium below 20 K[1]) which have spiral modulation in addition to a permanent magnetic moment.

Helimagnetism was first proposed in 1959, as an explanation of the magnetic structure of manganese dioxide.[2] Initially applied to neutron diffraction, it has since been observed more directly by Lorentz electron microscopy.[3] Some helimagnetic structures are reported to be stable up to room temperature.[4] Many helimagnets have a chiral cubic structure, such as the B20 crystal structure type.

Like how ordinary ferromagnets have domain walls that separate individual magnetic domains, helimagnets have their own classes of domain walls which are characterized by topological charge.[5]

Helimagnetic materials
Material Temperature range
FeGe,[4] –278 K.
MnGe[6] –170 K.
MnSi,[7] –29 K.
FexCo1-x (0.3 ≤ x ≤ 0.85)[8]
Cu2OSeO3[9] –58 K.
Fe1-xCoxSi (x = 0.2)[10]
Tb[11] 219–231 K.
Dy[12] 85–179 K.
Ho[13] 20–132 K.

See also

References
  1. Perreault, Christopher S.; Vohra, Yogesh K.; dos Santos, Antonio M.; Molaison, Jamie J. (2020). "Neutron diffraction study of magnetic ordering in high pressure phases of rare earth metal holmium". Journal of Magnetism and Magnetic Materials. Elsevier BV. 507: 166843. doi:10.1016/j.jmmm.2020.166843. ISSN 0304-8853.
  2. Yoshimori, Akio (1959-06-15). "A New Type of Antiferromagnetic Structure in the Rutile Type Crystal". Journal of the Physical Society of Japan. Physical Society of Japan. 14 (6): 807–821. doi:10.1143/jpsj.14.807. ISSN 0031-9015.
  3. Uchida, Masaya; Onose, Yoshinori; Matsui, Yoshio; Tokura, Yoshinori (2006-01-20). "Real-Space Observation of Helical Spin Order". Science. American Association for the Advancement of Science (AAAS). 311 (5759): 359–361. doi:10.1126/science.1120639. ISSN 0036-8075.
  4. Zhang, S. L.; Stasinopoulos, I.; Lancaster, T.; Xiao, F.; Bauer, A.; et al. (2017-03-09). "Room-temperature helimagnetism in FeGe thin films". Scientific Reports. Springer Science and Business Media LLC. 7 (1): 123. doi:10.1038/s41598-017-00201-z. ISSN 2045-2322.
  5. Schoenherr, P.; Müller, J.; Köhler, L.; Rosch, A.; Kanazawa, N.; Tokura, Y.; Garst, M.; Meier, D. (2018-03-05). "Topological domain walls in helimagnets". Nature Physics. Springer Science and Business Media LLC. 14 (5): 465–468. doi:10.1038/s41567-018-0056-5. ISSN 1745-2473.
  6. Martin, N.; Mirebeau, I.; Franz, C.; Chaboussant, G.; Fomicheva, L. N.; Tsvyashchenko, A. V. (2019-03-13). "Partial ordering and phase elasticity in the MnGe short-period helimagnet". Physical Review B. American Physical Society (APS). 99 (10): 100402(R). doi:10.1103/physrevb.99.100402. ISSN 2469-9950.
  7. Stishov, Sergei M; Petrova, A E (2011-11-30). "Itinerant helimagnet MnSi". Physics-Uspekhi. Uspekhi Fizicheskikh Nauk (UFN) Journal. 54 (11): 1117–1130. doi:10.3367/ufne.0181.201111b.1157. ISSN 1063-7869.
  8. Watanabe, Hideki; Tazuke, ichi; Nakajima, Haruo (1985-10-15). "Helical Spin Resonance and Magntization Measurement in Itinerant Helimagnet FexCo1-xSi(0.3≤x≤0.85)". Journal of the Physical Society of Japan. Physical Society of Japan. 54 (10): 3978–3986. doi:10.1143/jpsj.54.3978. ISSN 0031-9015.
  9. Seki, S.; Yu, X. Z.; Ishiwata, S.; Tokura, Y. (2012-04-12). "Observation of Skyrmions in a Multiferroic Material". Science. American Association for the Advancement of Science (AAAS). 336 (6078): 198–201. doi:10.1126/science.1214143. ISSN 0036-8075.
  10. Bannenberg, L. J.; Kakurai, K.; Falus, P.; Lelièvre-Berna, E.; Dalgliesh, R.; et al. (2017-04-28). "Universality of the helimagnetic transition in cubic chiral magnets: Small angle neutron scattering and neutron spin echo spectroscopy studies of FeCoSi". Physical Review B. American Physical Society (APS). 95 (14): 144433. doi:10.1103/physrevb.95.144433. ISSN 2469-9950.
  11. Palmer, S. B.; Baruchel, J.; Farrant, S.; Jones, D.; Schlenker, M. (1982). "Observation of Spiral Spin Antiferromagnetic Domains in Single Crystal Terbium". The Rare Earths in Modern Science and Technology. Boston, MA: Springer US. pp. 413–417. doi:10.1007/978-1-4613-3406-4_88. ISBN 978-1-4613-3408-8.
  12. Herz, R.; Kronmüller, H. (1978-06-16). "Field-induced phase transitions in the helical state of dysprosium". Physica Status Solidi (a). Wiley. 47 (2): 451–458. doi:10.1002/pssa.2210470215. ISSN 0031-8965.
  13. Tindall, D. A.; Steinitz, M. O.; Kahrizi, M.; Noakes, D. R.; Ali, N. (1991-04-15). "Investigation of the helimagnetic phases of holmium in ac‐axis magnetic field". Journal of Applied Physics. AIP Publishing. 69 (8): 5691–5693. doi:10.1063/1.347913. ISSN 0021-8979.
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