151Eu and 57Fe Mössbauer studies of EuCoO3

Evidence of spin transition and charge order in cobalt substituted La0.7Ca0.3MnO3

“…The lower transition temperature T 1 occurs due to the change from the high spin to the low spin state and depends on the difference between the energies of the Co ions in the two spin states in the crystal field, E = (E 3+ Co − E III Co ). As T 1 lies between 20 and 50 K in the present system E ∼ 10 meV as suggested for LaCoO 3 by some investigators [14]. The agreement between theory and experiment proves the prediction of de Gennes [18] that the system adopts the B type or A type of spin order depending on the relative strength of the DE and SE which is a function of the number of mobile carriers.…”

“…The possible spin arrangement type is given in the last column. [14,15]. In these systems it is suggested that cobalt ions exist predominantly in the low spin (t 6 2g e 0 g ) Co III state ( 1 A 1g ) at low temperatures and transform to the high spin state (t 4 2g e 2 g ) Co 3+ state ( 3 T 2g ) gradually up to ∼200 K. For x = 0.5 the region AF I (T 1 < T < T N ) is semiconducting but AF II (0 < T < T 1 ) is insulating (figure 1).…”

“…Jadhao et al [14] have shown through Mossbauer spectroscopy that the energy gap between the low spin and high spin states in EuCoO 3 is 20 meV which is comparable to the energy difference suggested by Raccah and Goodenough for LaCoO 3 as E 3+ Co − E III Co 80 meV [15]. We find that below T 1 ∼ 50 K the Co 3+ spins begin to change to the Co III state as the latter lies lower in energy than the high spin state in La 0.7 Ca 0.3 Mn 1−x Co x O 3 and at 0 K it is entirely in the low spin state.…”

Magnetic and transport studies in La1−xCaxMn0.7Co0.3O3 (0.1⩽x⩽0.5)

“…Jadhao et al [13] have shown through Mossbauer spectroscopy that the energy gap between the low-spin, Co III and high-spin, Co 3+ Table 1.…”

Some interesting phase transitions in solids

“…We have been investigating these electronic transitions in sever~l rare earth cobaltates of the general formula, LnCoOs. We have employed MiSssbauer spectroscopy and a variety of other techniques to study the transitions (see for example Jadhao et al 1976). The studies have enabled us not only to follow the nature of changes occurring in cobalt states, but also to underscore the role of the rare earth ion.…”