Unified molecular field theory for collinear and noncollinear Heisenberg antiferromagnets
In this study, a unified molecular field theory (MFT) is presented that applies to both collinear and planar noncollinear Heisenberg antiferromagnets (AFs) on the same footing. The spins in the system are assumed to be identical and crystallographically equivalent. This formulation allows calculations of the anisotropic magnetic susceptibility χ versus temperature T below the AF ordering temperature T _{N} to be carried out for arbitrary Heisenberg exchange interactions J _{ij} between arbitrary neighbors j of a given spin i without recourse to magnetic sublattices. The Weiss temperature θ _{p} in the Curie-Weiss law is written in terms of the J _{ij} values and T _{N} in terms of the J _{ij} values and an assumed AF structure. Other magnetic and thermal properties are then expressed in terms of quantities easily accessible from experiment as laws of corresponding states for a given spin S. For collinear ordering these properties are the reduced temperature t=T/T _{N}, the ratio f = θ _{p}/T _{N}, and S. For planar noncollinear helical or cycloidal ordering, an additional parameter is the wave vector of the helix or cycloid. The MFT is also applicable to AFs with other AF structures. The MFT predicts that χ(T ≤ Tmore »
- Publication Date:
- Report Number(s):
- IS-J-8629
Journal ID: ISSN 1098-0121; PRBMDO
- Grant/Contract Number:
- AC02-07CH11358
- Type:
- Accepted Manuscript
- Journal Name:
- Physical Review. B, Condensed Matter and Materials Physics
- Additional Journal Information:
- Journal Volume: 91; Journal Issue: 6; Journal ID: ISSN 1098-0121
- Publisher:
- American Physical Society (APS)
- Research Org:
- Ames Laboratory (AMES), Ames, IA (United States)
- Sponsoring Org:
- USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 36 MATERIALS SCIENCE
- OSTI Identifier:
- 1227216
- Alternate Identifier(s):
- OSTI ID: 1180925
Johnston, David C. Unified molecular field theory for collinear and noncollinear Heisenberg antiferromagnets. United States: N. p.,
Web. doi:10.1103/PhysRevB.91.064427.
Johnston, David C. Unified molecular field theory for collinear and noncollinear Heisenberg antiferromagnets. United States. doi:10.1103/PhysRevB.91.064427.
Johnston, David C. 2015.
"Unified molecular field theory for collinear and noncollinear Heisenberg antiferromagnets". United States.
doi:10.1103/PhysRevB.91.064427. https://www.osti.gov/servlets/purl/1227216.
@article{osti_1227216,
title = {Unified molecular field theory for collinear and noncollinear Heisenberg antiferromagnets},
author = {Johnston, David C.},
abstractNote = {In this study, a unified molecular field theory (MFT) is presented that applies to both collinear and planar noncollinear Heisenberg antiferromagnets (AFs) on the same footing. The spins in the system are assumed to be identical and crystallographically equivalent. This formulation allows calculations of the anisotropic magnetic susceptibility χ versus temperature T below the AF ordering temperature TN to be carried out for arbitrary Heisenberg exchange interactions Jij between arbitrary neighbors j of a given spin i without recourse to magnetic sublattices. The Weiss temperature θp in the Curie-Weiss law is written in terms of the Jij values and TN in terms of the Jij values and an assumed AF structure. Other magnetic and thermal properties are then expressed in terms of quantities easily accessible from experiment as laws of corresponding states for a given spin S. For collinear ordering these properties are the reduced temperature t=T/TN, the ratio f = θp/TN, and S. For planar noncollinear helical or cycloidal ordering, an additional parameter is the wave vector of the helix or cycloid. The MFT is also applicable to AFs with other AF structures. The MFT predicts that χ(T ≤ TN) of noncollinear 120° spin structures on triangular lattices is isotropic and independent of S and T and thus clarifies the origin of this universally observed behavior. The high-field magnetization and heat capacity for fields applied perpendicular to the ordering axis (collinear AFs) and ordering plane (planar noncollinear AFs) are also calculated and expressed for both types of AF structures as laws of corresponding states for a given S, and the reduced perpendicular field versus reduced temperature phase diagram is constructed.},
doi = {10.1103/PhysRevB.91.064427},
journal = {Physical Review. B, Condensed Matter and Materials Physics},
number = 6,
volume = 91,
place = {United States},
year = {2015},
month = {2}
}