Volume 86, Number 6, June 2009
Article Number 67005
Number of page(s) 5
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
Published online 09 July 2009
EPL, 86 (2009) 67005
DOI: 10.1209/0295-5075/86/67005

Theory of magnetic order in Fe1+yTe1-xSex

Chen Fang1, B. Andrei Bernevig2 and Jiangping Hu1

1   Department of Physics, Purdue University - West Lafayette, IN 47907, USA
2   Princeton Center for Theoretical Science, Princeton University - Princeton, NJ 08544, USA

received 26 January 2009; accepted in final form 25 May 2009; published June 2009
published online 9 July 2009

We develop a local spin model to explain the rich magnetic structures in the iron-based superconductors Fe1+yTe1-xSex. We show that our model exhibits both commensurate antiferromagnetic and incommensurate magnetic order along the crystal a-axis. The transition from the commensurate to the incommensurate phase is induced when the concentration of excess Fe atoms is larger than a critical value. Experimentally measurable spin-wave features are calculated, and the mean-field phase diagram of the model is obtained. Our model also suggests the existence of a large quantum critical region due to strong spin frustration upon increasing Se concentration.

74.25.Ha - Magnetic properties.
71.10.-w - Theories and models of many-electron systems.
71.27.+a - Strongly correlated electron systems; heavy fermions.

© EPLA 2009