Magnetic, Electrical Properties and Spin-Glass Effect of Substitution of Ca for Pr in Ca2-xPrxMnO4 Compounds

Abstract

Ca 2-x Pr x MnO 4 (x = 0.000 to 0.200) manganites were synthesized by a sol-gel method and then characterized by X-ray diffraction (XRD) at room temperature. Rietveld refinement technique shows that all samples can be indexed in orthorhombic system except for Ca 2 MnO 4 (x = 0.000) which can be indexed in the tetragonal system. Magnetic and electrical measurements show that magnetization and resistivity have a large dependence of the fractional composition x and temperature. The applied magnetic field has also a large influence on magnetization level. Spin-glass behavior was detected at low temperature for the samples with x 0.175. For all x-values, all compounds exhibit semiconductor behavior and the ferromagnetic (FM) transition temperature T C (Curie temperature) is around 105 K, whatever the applied field.

Charge ordering analysis by electrical and dielectric measurements in Ca2−xPrxMnO4 (x=0–0.2) compounds

“…5-inset, we can conclude that, for high x-values, as reported in our previous work [23], local antiferromagnetic (AFM) interactions, induced by higher Pr-content, become important and compete with the long-range FM from the DE interactions between Mn ions. Thus, the dc resistivity versus Pr-doping content (x) undergoes an increase.…”

“…The X-ray diffraction (XRD) spectra at room temperature had been published in our previous work [23]. We have found that all samples are single phase with a perovskite-related K 2 NiF 4 structure.…”

“…15 for x = 0) leads to the appearance of a ferromagnetic phase at T < T C [15,18]. Such behavior is induced by Mn 3+ -O-Mn 4+ systems having a ferromagnetic (FM) coupling [19,23]. As known, in both A 1−x B x MnO 3 and A 2−x B x MnO 4 manganite materials, the substitution of a divalent A-ion by a trivalent B-ion induces a mixed valence Mn 3+ /Mn 4+ , enhancing the conduction by e g electrons hopping through Mn 3+ -O-Mn 4+ system [26,27].…”

Structural and Magnetic Studies of Ca2−x Sm x MnO Compounds (x=0–0.4)

“…4) were indexed with a tetragonal structure (I/4mmm space group) [27]. This transition type is also observed with other rare-earth doping, as Pr [28], Nd and Y [29].…”

“…The T N and T C temperature values are listed in Table 3. For non-doped compound (x = 0), the magnetization is almost zero [28]. By Sm-doping until x = 0.1, the magnetization increases rapidly.…”