Antisite disorder

The commonest form of disorder among the B-site cations results in the B- and B -cations swapping positions, an example of antisite disorder. Antisite disorder is temperature sensitive and is often influenced by the preparation methods employed and the particle size of the product, with nanoparticles often having different surface ordering than bulk samples. These defects have consequences for the electronic and magnetic properties of the phase. 

Antisite disorder Exchange of two atoms from their regular site to that of the other in the lattice 0... 

It is important to note that the samples of LixMn2(Mo04)3, nanoscaled samples, synthesized by solvothermal method are free from the anti-site disorder resonance signal, which is observed in micro-scaled Li2Mn2(Mo04)3 samples. The appearance of antisite disorder defects is associated with location of Mn + in lithium interstitial positions. It impedes the diffusion of Li+ in crystal structure of cathodic materials that have the negative influence on their electrochemical performance. Thus, the ESR investigations... 

More complex defect models were also considered for LaMnOs suggesting antisite disordering (i.e. incorporation of Mn cations into La vacancies) [24, 25]. 

The anion sublattice is occupied only by As atoms, while the cation sublattice is occupied by Ga and Mn atoms, and also by As antisite defects. We consider only substitutional disorder on the cation sublattice which in turn is described within the coherent potential approximation (CPA) . We thus neglect local environment effects and lattice relaxations. 

In Fig. 11 we demonstrate the dramatic effect of As-antisites on exchange interactions. The first nearest-neighbor interaction is reduced by nearly an order of magnitude as compared to the case without antisites while the reduction of other interactions is less pronounced. The Curie temperature drops from 289 K for the case without As-antisites to 126 K for the case with As-antisites. The reduction of JMn.Mn reasons as it can be seen from Eq. (3) (i) the most important is the change of the number of carriers which enters the expression (3) via the value of the Fermi energy (see Figs. 9 and 11) (ii) the disorder due to various impurities influences the quantity " and, in particular, its values close to the Fermi energy whose contribution to... 

For most of the intermetallic compounds, deviation from the stoichiometric composition is accommodated by antisite atoms CuZn, CusAu, NiTi, NisAl. Paired antisite defects are also formed thermally in high concentration for those alloys which present an order-disorder transition in the solid state (CU3AU, CuZn) their concentration is directly related to the LRO parameter value. The absence of structural vacancies has been checked by positron annihilation in the case of CuZn (Kim and Buyers, 1980), CujAu (Doyama et fl/.,1985a,b), FejAl (Schaefer et al., 1990), and TiAl (Shirai and Yamaguchi, 1992). In all cases, thermal vacancies form at high temperature. 

Figure 1. Schematic of a lattice of an intermetallic compound containing Frenkel defects (vacancies and interstitial atoms) as well as regions of chemical disorder in which there are antisite defects...

---