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The relation between magnetization and internal energy for ferromagnets Fe, Ni, and electron‐doped In 2 O 3 :Cr, antiferromagnetically ordered Zn Cu 3 (OH) 6 Cl 2 , and the layered material κ‐(BEDT‐TTF) 2 Cu[N(CN) 2 ]Cl
Author(s) -
March N. H.
Publication year - 2009
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.22265
Subject(s) - antiferromagnetism , ferromagnetism , condensed matter physics , magnetization , ising model , exchange interaction , electron , spin (aerodynamics) , physics , spontaneous magnetization , chemistry , materials science , magnetic field , thermodynamics , quantum mechanics
Grout and March utilized the exact solution of the two‐dimensional Ising model to relate the internal energy E ( T ) to the magnetization M ( T ). These authors then used Bloch spin‐wave theory to relate E and M at low temperatures for both insulating and metallic ferromagnets in three dimensions. Ayuela and March, very recently, have used experimental data on the specific heat and the magnetization to show that for metallic Fe and Ni the E – M data collapse on to a single curve. A model with long‐range exchange interactions is presented to allow insight to be gained into this feature. Reference is also made briefly to the ferromagnetism of the electron‐doped In 2 O 3 :Cr system. Two antiferromagnetically ordered materials are next considered, though now more qualitatively than for the ferromagnets. The first is the spin −1/2 kagome antiferromagnet ZnCu 3 (OH) 6 Cl 2 , and the second is the κ‐phase layered material (BEDT‐TTF) 2 Cu[N(CN) 2 ]Cl. Anomalous low‐temperature specific heat C v ( T ) is emphasized, with an enhancement that is reduced by application of a magnetic field. Further work is proposed, both experiment and theory, to understand the precise nature of the low‐lying magnetic excitations in the latter κ‐phase material. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009