期刊
JOURNAL OF ALLOYS AND COMPOUNDS
卷 847, 期 -, 页码 -出版社
ELSEVIER SCIENCE SA
DOI: 10.1016/j.jallcom.2020.156297
关键词
Manganite; Doping effect; Optical; Magnetic; Resistivity
资金
- Department of Science and Technology (DST), Government of India [INT/RUS/RFBR/P-239]
- Indo-Russian project (RFBR) [16-53-45010]
- Government of the Russian Federation [02.A03.21.0006]
The effect of A-site doping by alkaline earth metals (A = Ca, Sr and Ba) on optical, magnetic, and electrical properties of Nd(1-x)A(x)Mn(0.5)Fe(0.5)O(3-delta) (x = 0, 0.25) has been investigated. The UV-vis absorption spectra show that the A-site doping decreases the absorption. Two values of optical band-gap energy (E-g) can be estimated for each studied sample: the higher E-g value is associated with the charge transfer involving iron cations and the lower E-g value - with the charge transfer via manganese cations. Partial substitution of neodymium by alkaline earth metals decreases the Neel temperature (T-N) and induces significant irreversibility between the zero-field cooled (ZFC) and field-cooled (FC) data below T-N. The field-dependent magnetization at 3 K indicates antiferromagnetic ordering with a spin canting. Temperature dependencies of resistivity demonstrate the change from metallic to semiconductor-type conduction (with increasing temperature) at T = T-p < T-N. The T-p temperature significantly decreases with doping. The introduction of alkaline earth metals in Nd(1-x)A(x)Mn(0.5)Fe(0.5)O(3-delta) noticeably reduces the resistivity in the semiconducting region. The small polaron hopping (SPH) mechanism of conduction is suggested at T > T-N. Within the range of T-p < T < T-N, the resistivity data are interpreted by the variable range hopping (VRH) mechanism. A significant value of magnetoresistance (similar to 44%) is observed only for Nd(0.75)Sr(0.25)Mn(0.5)Fe(0.5)O(3-delta )at 120 K. (C) 2020 Elsevier B.V. All rights reserved.
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