[Wien] Why the antiferromagnetic structure of Cr is still cubic

[Stefaan Cottenier]

> In general, any magnetic ordering breaks the symmetry of the system, and
> structural distortions compatible with the new symmetry can happen due
> to magneto-structural coupling. Often this coupling is too weak to be
> detected, but in other cases like NiO is strong enough.

And this is indeed what happens for bcc Cr (where the initial question 
was about). Quoting from pages 173-174 of "Phase diagrams of the 
elements" (David A. Young):

"At room pressure and temperature, Cr is bcc. This structure is modified 
very slightly by two first order magnetic phase transitions. From 0 to 
123 K, Cr is antiferromagnetic with a small tetragonal distortion of the 
bcc lattice. From 123 K to 311 K, Cr is antiferromagnetic with as small 
orthorhombic distortion of the bcc lattice."

The original experiments can be found in 
http://journals.aps.org/prl/pdf/10.1103/PhysRevLett.23.979

Stefaan


-- 
Stefaan Cottenier
Center for Molecular Modeling (CMM) &
Department of Materials Science and Engineering (DMSE)
Ghent University
Tech Lane Ghent Science Park – Campus A
building 903
BE-9052 Zwijnaarde
Belgium

http://molmod.ugent.be
http://www.ugent.be/ea/dmse/en
email: stefaan.cottenier at ugent.be

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