Electron doping induced magnetic glassy state in phase separated YBaCo2O5.5-δ

Abstract

The structural, magnetic and transport properties of the layered RBaCo2O5.5±δ cobaltites are sensitive to the oxygen stoichiometry. In this present study, we report the presence of a low-temperature magnetic glassy state in electrondoped polycrystalline YBaCo2O5.5 cobaltite. The ac magnetization studies show the absence of conventional spin glass features, while the various dc magnetization studies demonstrate the presence of non-equilibrium magnetic glassy state at low temperature. The magnetic glassy state of this sample results from the kinetic arrest of the first order ferro (or ferri) to antiferromagnetic transition. The role of electron doping in the occurrence of magnetic glassy phenomena is discussed in terms of magnetic phase separation involving the Co 3+ /Co 2+ clusters of the ferrimagnetic phase in the Co 3+ /Co 3+ antiferromagnetic matrix.

Magnetic glassy state at low spin state of Co3+ in EuBaCo2O5+δ (δ = 0.47) cobaltite

“…On the other hand, the formation of MG is also reported in the layered YBaCo 2 O 5+δ (δ = 0.50) cobaltite with 5% Ca substitution at Y and Ba sites [10]. In complement to the Ca substitution studies, we have shown that the electron doped YBaCo 2 O 5.5−δ (δ = 0.13) cobaltite also showed the presence of MG state at low temperature (T) [17]. However, magneto structural coupling hardly plays a role in both the cobaltites and the MG phenomenon is explained considering the local phase separation of FM and AFM clusters.…”

“…Finally, it is worth to compare the MG state of the present EBCO with the other available reports of this cobaltite family. The MG state is reported in the YBaCo2O5+δ (δ = 0.50) cobaltite with 5% Ca substitution at Y and Ba sites [10] and also in the electron doped YBaCo2O5.5-δ (δ = 0.13) [18] , where the arrested phase has very low magnetization. The isothermal magnetic entropy studies also show the large entropy change at the kinetically arrested phase.…”

“…Finally, it is worth to compare the MG state and the kinetic arrest of the present EBCO with the other available reports on the cobaltite, manganite and Heusler families. The MG state is reported in YBaCo 2 O 5+δ (δ = 0.50) cobaltite with 5% Ca substitution at Y and Ba sites [10], Gd 1−x Ca x BaCo 2 O 5.5 (x = 0 and 0.02) cobaltite [34], electron doped YBaCo 2 O 5.5−δ (δ = 0.13) cobaltite [17], Heusler compound of Mn 2 PtGa [11], single crystals Gd 0.5 Sr 0.5 MnO 3 [35] and others. Although the MG state and kinetic arrest are observed for all samples at low T, but the high T magnetic state is very different in the case of EBCO as compared to the above samples.…”