| Issue |
Europhys. Lett.
Volume 54, Number 4, May 2001
|
|
|---|---|---|
| Page(s) | 508 - 514 | |
| Section | Condensed matter: electronic structure, electrical, magnetic, and optical properties | |
| DOI | https://doi.org/10.1209/epl/i2001-00276-4 | |
| Published online | 01 December 2003 | |
Direct observation of the quantum energy gap in 
tetragonal cuprate antiferromagnets
1
RIKEN (The Institute of Physical and Chemical
Research) Wako, Saitama 351-0198, Japan
2
School of Physics and Astronomy, Sackler Faculty of
Exact Sciences Tel Aviv University - Tel Aviv
69978, Israel
3
Center of Materials Science and Engineering,
Massachusetts Institute of Technology Cambridge, MA
02139, USA
4
University of Toronto - Toronto, ON, Canada, M5S 1A1
Received:
26
January
2001
Accepted:
6
March
2001
Using an electron spin resonance spectrometer covering a wide
range of frequency and magnetic field, we have measured the
low-energy excitations of the 
tetragonal
antiferromagnets, 
and
. Our observations of in-plane
energy gaps of order 0.1
at zero external magnetic field
are consistent with a spin-wave calculation, which includes
several kinds of quantum fluctuations that remove frustration.
Such gaps vanish for classical spins, and were too small to be
observed by other techniques. Results agree with other
experiments and with exchange anisotropy parameters determined
from a five-band Hubbard model.
PACS: 74.50.+g – Ferromagnetic, antiferromagnetic and ferromagnetic resonances; spin-wave resonance / 75.10.Jm – Quantized spin models / 75.50.Ee – Antiferromagnetics
© EDP Sciences, 2001
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