Abstract
A computational study of the electronic structure and magnetic properties of Gd pnictides is reported. The calculations were performed using a full-potential linear muffin-tin orbital method within the so-called approach, which adds Hubbard- correlation effects to specified narrow bands in a mean-field approach to the local spin-density approximation (LSDA). Here both the and 5 states are subject to such corrections. The values were determined semiempirically by using photoemission and inverse photoemission data for , , , and . In contrast to which represents narrow-band physics, represents a quasiparticle self-energy correction of the LSDA gap underestimate. The value was adjusted using optical-absorption data for semiconducting above its Curie temperature. Below the Curie temperature, however, in the ferromagnetic state, the gap becomes almost zero. The other Gd pnictides are found to have a small overlap of the conduction band at the point and the valence band at the point in the majority-spin channel. A small gap opens in the spin-minority channel of and , which are thus half metallic. This spin-minority gap closes in semimetallic and . While is found to be ferromagnetic, the other Gd pnictides are found to be antiferromagnetic, with ordering along [111]. From calculations with different magnetic configurations, a Heisenberg model with first and second nearest-neighbor exchange parameters is extracted. The Heisenberg model is then used to predict Curie-Weiss and Néel temperatures and critical magnetic fields within mean field and compared with experimental data. The trends are found to be in good agreement with the experimental data.
2 More- Received 14 April 2006
DOI:https://doi.org/10.1103/PhysRevB.74.085108
©2006 American Physical Society