Volume 54, Number 4, May 2001
|Page(s)||508 - 514|
|Section||Condensed matter: electronic structure, electrical, magnetic, and optical properties|
|Published online||01 December 2003|
Direct observation of the quantum energy gap in tetragonal cuprate antiferromagnets
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
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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