Bond-valence analysis on the structural effects in magnetoresistive manganese perovskites

Abstract

For the perovskites that show colossal-magnetoresistance (CMR) behaviour, we use the global instability index, R1, as a measure of the influence of the static lattice effects on the magnetic and electrical properties. These effects arise from the size mismatch between the ions at A and Mn sites as well as the size distribution of ions at A sites. A magnetic and electronic phase diagram as a function of R1 for (R = trivalent rare-earth ions, alkaline-earth ions) reveals four well-defined regions: paramagnetic insulator (PMI), ferromagnetic metal (FMM), spin glass or ferromagnetic insulator (FMI), and a transition region (TMI), in which the compounds exhibit a variety of behaviours.

Structural, magnetic and dielectric properties of La2−xCaxNiO4+δ (x=0, 0.1, 0.2, 0.3)

“…Formal valence of ion and the deviation valence are described as V i and d i [21][22][23][24][25]. Tolerance factor reflects the stability of structure and the structure is stable if t is close to 1.…”

Structural stability and electronic properties of Ba2MIrO6 (M=La, Y) by first principles

“…On the other hand, we calculated the oxidation or valence state of each element and global stability R1 for the two compounds by use of an empirical method, i.e., the bond valence model [13][14][15][16][17]. This is an empirical model which provides a useful and quantitative description of inorganic bonding.…”

Evolution of the structure, microstructure and physical properties of RuSr2GdCu2O8 as a function of the thermal treatment

“…The results of the bond valence sum (BVS) calculations [17] carried out using the refined cell data are reported in Table 2; it is worth to note that in RuSr 2 GdCu 2 O 8 both Cu and Ru are characterised by mixed valence and it cannot be excluded that the ratio between the different cationic species can be slightly dependent on sample preparation.…”

“…As The global instability index [17] (GII) derived from the BVS values is also reported: its value indicates that the structure is almost unstrained. In fact for unstrained structures GII < 0.1 vu, whereas larger value of GII are indicative of strained bonds that can induce instabilities in the lattice (for GII > 0.2 the structure may be incorrect or refined in a space group with too high symmetry) [17].…”