## Quantum and Low-Dimensional Magnetism

Magnetism of condensed matter systems is a fundamentally quantum
phenomenon - it originates from the Pauli principle governing
electron's behavior and was only explained with the advent of quantum
mechanics. Nevertheless, many properties of common magnetic materials
whose magnetism mainly arises from magnetization associated with total
spin angular momentum (quantum number) of atomic electrons, which is
large compared to ħ,
can be understood on the (semi)classical level, neglecting quantum
fluctuations.

The situation is dramatically different in magnets where spins are
small, ħS
= ħ/2
or ħS
= ħ,
and interactions are quasi one- or two- dimensional (1D or 2D). In the
ideal case, where spin coupling is strictly 1D, spin system with
spin-isotropic interactions never orders, even at T=0, while in 2D
magnetic order disappears at any finite temperature. This is a
well-known Mermin-Wagner theorem, which extends to magnets a similar
statement due to Peierls and Landau on the instability of
low-dimensional crystals. When
they order due to residual 3D and/or anisotropic interactions, magnets
with small spins, like crystals made of light atoms, exhibit
quantum-crystalline phases with weak order and large zero-point motion.

Our current research topics include:

Last Modified: Friday, 21-Mar-2008 18:22:59 EDT

Please forward all questions about this site to:
Igor Zaliznyak