Mössbauer and Magnetic Studies of Doped Lanthanum Manganite La1 – xCaxMn0.98Fe0.02O3 + δ (x = 0.05, 0.10, 0.20): I. Nonstoichiometric Composition

Resumo

Mössbauer and magnetic studies of Ca-doped lanthanum manganites La_1 – xCa_xMn_0.98Fe_0.02O_3 + δ (x = 0.05, 0.10, 0.20) of a nonstoichiometric composition are performed. An increase in the Ca concentration and a decrease in the interstitial oxygen quantity results in a decreasing electric-field gradient in the region of the Fe atomic nucleus due to the spatial rearrangement of the charge of surrounding atoms. The Mössbauer spectra of all studied lanthanum-manganite samples demonstrate a relaxation character at low temperatures, which can be associated with the presence of small-sized magnetic clusters. This finding correlates with the results of magnetic investigations. The values of the coercive force, saturation magnetization, and blocking temperature are determined.