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Helimagnetism

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LorentzTEMimage of helical spin stripes iniron germanide(FeGe) at 90 K

Helimagnetismis a form of magnetic ordering where spins of neighbouringmagnetic momentsarrange themselves in a spiral or helical pattern, with a characteristic turn angle of somewhere between 0 and 180 degrees. It results from the competition betweenferromagneticandantiferromagneticexchange interactions.[citation needed]It is possible to view ferromagnetism and antiferromagnetism as helimagnetic structures with characteristic turn angles of 0 and 180 degrees respectively. Helimagnetic order breaks spatialinversion 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 ofantiferromagnet.This distinguishes helimagnets fromconical magnets,(e.g.Holmiumbelow 20 K[1]) which have spiral modulation in addition to a permanent magnetic moment. Helimagnets can be characterized by the distance it takes for the spiral to complete one turn. In analogy to thepitch of screw thread,the period of repetition is known as the "pitch" of the helimagnet. If the spiral's period is somerationalmultiple of the crystal's unit cell, the structure iscommensurate,like the structure originally proposed for MnO2.[2]On the other hand, if the multiple is irrational, the magnetism is incommensurate, like the updated MnO2structure.[3]

Helimagnetism was first proposed in 1959, as an explanation of themagnetic structureofmanganese dioxide.[2]Initially applied toneutron diffraction,it has since been observed more directly by Lorentz electron microscopy.[4]Some helimagnetic structures are reported to be stable up to room temperature.[5]Like how ordinary ferromagnets havedomain wallsthat separate individual magnetic domains, helimagnets have their own classes of domain walls which are characterized bytopological charge.[6]

Many helimagnets have a chiral cubic structure, such as the FeSi (B20)crystal structure type.In these materials, the combination of ferromagnetic exchange and theDzyaloshinskii–Moriya interactionleads to helixes with relatively long periods. Since the crystal structure is noncentrosymetric even in the paramagnetic state, the magnetic transition to a helimagnetic state does not break inversion symmetry, and the direction of the spiral is locked to the crystal structure.

On the other hand, helimagnetism in other materials can also be based onfrustrated magnetismor theRKKY interaction.The result is thatcentrosymmetricstructures like the MnP-type (B31) compounds can also exhibit double-helix type helimagnetism where both left and right handed spirals coexist.[7]For these itinerant helimagnets, the direction of the helicity can be controlled by applied electric currents and magnetic fields.[8]

Helimagnetic materials
Material Temperature range Space group
β-MnO2[2][3] < 93 K P42/mnm
FeGe,[5] < 278 K P213
MnGe[9] < 170 K P213
MnSi,[10] < 29 K P213
FexCo1−xSi (0.3 ≤ x ≤ 0.85)[11][12] P213
Cu2OSeO3[13] < 58 K P213
FeP[7] < 120 K Pnma
FeAs[14] < 77 K Pnma
MnP[15] < 50 K Pnma
CrAs[16] < 261 K Pnma
CrI2[17] < 17 K Cmc21
FeCl3[18] < 9 K R3
NiBr2[19] < 22 K R3m
NiI2[20] < 75 K R3m
Cr1/3NbS2[21][22] < 127 K P6322
Tb[23] 219–231 K P63/mmc
Dy[24] 85–179 K P63/mmc
Ho[25] 20–132 K P63/mmc

See also

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References

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  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.507.Elsevier BV: 166843.Bibcode:2020JMMM..50766843P.doi:10.1016/j.jmmm.2020.166843.OSTI1607351.
  2. ^abcYoshimori, Akio (1959). "A New Type of Antiferromagnetic Structure in the Rutile Type Crystal".Journal of the Physical Society of Japan.14(6). Physical Society of Japan: 807–821.Bibcode:1959JPSJ...14..807Y.doi:10.1143/jpsj.14.807.
  3. ^abRegulski, M.; Przeniosło, R.; Sosnowska, I.; Hoffmann, J.-U. (2003-11-03). "Incommensurate magnetic structure of β−MnO2".Physical Review B.68(17). American Physical Society (APS): 172401.doi:10.1103/physrevb.68.172401.ISSN0163-1829.
  4. ^Uchida, Masaya; Onose, Yoshinori; Matsui, Yoshio; Tokura, Yoshinori (2006). "Real-Space Observation of Helical Spin Order".Science.311(5759). American Association for the Advancement of Science (AAAS): 359–361.Bibcode:2006Sci...311..359U.doi:10.1126/science.1120639.PMID16424334.S2CID37875453.
  5. ^abZhang, S. L.; Stasinopoulos, I.; Lancaster, T.; Xiao, F.; Bauer, A.; et al. (2017)."Room-temperature helimagnetism in FeGe thin films".Scientific Reports.7(1). Springer Science and Business Media LLC: 123.Bibcode:2017NatSR...7..123Z.doi:10.1038/s41598-017-00201-z.PMC5427977.PMID28273923.
  6. ^Schoenherr, P.; Müller, J.; Köhler, L.; Rosch, A.; Kanazawa, N.; Tokura, Y.; Garst, M.; Meier, D. (2018). "Topological domain walls in helimagnets".Nature Physics.14(5). Springer Science and Business Media LLC: 465–468.arXiv:1704.06288.Bibcode:2018NatPh..14..465S.doi:10.1038/s41567-018-0056-5.S2CID119021621.
  7. ^abSukhanov, A. S.; Tymoshenko, Y. V.; Kulbakov, A. A.; Cameron, A. S.; Kocsis, V.; et al. (2022-04-20). "Frustration model and spin excitations in the helimagnet FeP".Physical Review B.105(13). American Physical Society (APS): 134424.arXiv:2201.10358.Bibcode:2022PhRvB.105m4424S.doi:10.1103/physrevb.105.134424.ISSN2469-9950.S2CID246276036.
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  11. ^Watanabe, Hideki; Tazuke, ichi; Nakajima, Haruo (1985). "Helical Spin Resonance and Magntization Measurement in Itinerant Helimagnet FexCo1−xSi (0.3≤x≤0.85) ".Journal of the Physical Society of Japan.54(10). Physical Society of Japan: 3978–3986.Bibcode:1985JPSJ...54.3978W.doi:10.1143/jpsj.54.3978.
  12. ^Bannenberg, L. J.; Kakurai, K.; Falus, P.; Lelièvre-Berna, E.; Dalgliesh, R.; et al. (2017)."Universality of the helimagnetic transition in cubic chiral magnets: Small angle neutron scattering and neutron spin echo spectroscopy studies of FeCoSi".Physical Review B.95(14): 144433.arXiv:1701.05448.Bibcode:2017PhRvB..95n4433B.doi:10.1103/physrevb.95.144433.S2CID31673243.
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  17. ^Schneeloch, John A.; Liu, Shunshun; Balachandran, Prasanna V.; Zhang, Qiang; Louca, Despina (2024-04-03). "Helimagnetism in the candidate ferroelectric CrI 2".Physical Review B.109(14): 144403.arXiv:2310.12120.doi:10.1103/PhysRevB.109.144403.ISSN2469-9950.
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  19. ^Adam, A; Billerey, D; Terrier, C; Katsumata, K; Magariño, J; Tuchendler, J (1980). "Magnetic resonance experiments in NiBr2 at high frequencies and high magnetic fields".Physics Letters A.79(4). Elsevier BV: 353–354.doi:10.1016/0375-9601(80)90369-2.ISSN0375-9601.
  20. ^Kuindersma, S.R.; Sanchez, J.P.; Haas, C. (1981). "Magnetic and structural investigations on NiI2 and CoI2".Physica B+C.111(2–3). Elsevier BV: 231–248.doi:10.1016/0378-4363(81)90100-5.ISSN0378-4363.
  21. ^Miyadai, Tomonao; Kikuchi, Katsuya; Kondo, Hiromitsu; Sakka, Shuzo; Arai, Masatoshi; Ishikawa, Yoshikazu (1983-04-15). "Magnetic Properties of Cr1/3NbS2".Journal of the Physical Society of Japan.52(4). Physical Society of Japan: 1394–1401.Bibcode:1983JPSJ...52.1394M.doi:10.1143/jpsj.52.1394.ISSN0031-9015.
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