151Eu Mössbauer Spectroscopy in La0.38Eu0.29Ca0.33MnO3

Abstract

Electrical conductivity with and without magnetic field, d.c. magnetization and 151 Eu Mössbauer studies were carried out in La 0.48 Eu 0.29 Ca 0.33 MnO 3 perovskite manganite system. An insulating ground state is found throughout the temperature range with charge ordered (CO) state emerging at T C0 õ 140 K, where as an external magnetic field of 6 T induces metalYinsulator transition at õ120 K. D.C. magnetization measurements show the antiferromagnetic (AFM) transition occurring at T N $ 48 K. The temperature dependent 151 Eu Mössbauer measurements showed that the substituted Eu replaces La 3+ in the 3+ charge state and a small magnetic moment gets induced at the Eu nucleus at low temperatures. The anomalous variation of the f-factor with temperature occurring around T N and T Co corroborates the occurrence of antiferromagnetic (AFM) and charge ordering (CO) transition, respectively.

Magnetic field-induced transitions in La0.42Eu0.25Ca0.33MnO3perovskite manganite

“…As mentioned above, a smaller ionic radius rare earth ion, such as Eu, doping into the LCMO system induces local structural distortions leading to the tilting of the MnO 6 octahedra. In our previous studies we found that the metal-insulator transition temperature decreases to 130 K in the La 0.50 Eu 0.17 Ca 0.33 MnO 3 system and to 78 K in the La 0.46 Eu x0.21 Ca 0.33 MnO 3 system [20,21]. The decrease in the lattice parameters was also observed with the increase in Eu content [20,21].…”

“…Electrical transport measurements in low magnetic fields show the melting of spin polarons with the increase in the magnetic field [19]. The 151 Eu Mossbauer studies in La 0.67−x Eu x Ca 0.33 MnO 3 suggest local structural re-ordering at phase transition boundaries supporting the intricate relation between the lattice, charge and spin degrees of freedom [10,20]. In many recent studies, a resistivity minimum was observed in manganites, no matter whether polycrystalline, quality film or single crystal, which is similar to the Kondo effect [21][22][23].…”

“…The refined lattice and atomic cell parameters are given in table 1. It can be seen from the XRD pattern that the sample is well characterized without detectable extra peaks appearing, indicating the sample is well crystallized and in good single [19,20,26]. A systematic decrease in the lattice parameters implies a gradual increase in the lattice deformation strength in the system with the increase in Eu content.…”

A change from second- to first-order transition in (La1−xEux)0.67Ca0.33MnO3(0 ≤x≤ 0.2)

“…The electrical transport measurements under low magnetic field of such compounds had shown melting of the spin polarons with the increase of magnetic field [16]. The 151 Eu Mössbauer studies in La 0.67−x Eu x Ca 0.33 MnO 3 suggested that the local structural reordering at phase transition boundaries supports the intricate relation between the lattice, charge and spin degree of freedom [17,18]. In a recent study, Reddy et al [19] reported that magnetic field induced transitions in La 0.42 Eu 0.25 Ca 0.33 MnO 3 manganites were due to strong competition between electron, phonon, charge and spin interactions.…”

151Eu Mössbauer studies on La0.5Eu0.17Ca0.33MnO3 CMR system

“…Spectroscopic studies based on neutron [10], EXAFs [11], µSR [12] reveals the role of JT phonons is vital in controlling the electrical transport. Partial replacement of La by Eu in this system is expected to reveal importance of the role of JT phonons play important role around phase transition boundaries in these materials [11,13].…”