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Title: Structural and magnetotransport properties of the Y doped A-site deficient double layered manganites La{sub 1.2−x}□{sub 0.2}Y{sub x}Ca{sub 1.6}Mn{sub 2}O{sub 7}

Abstract

We present structural, magnetic and electrical properties of the polycrystalline A-site-deficient yttrium doped double layered manganites La{sub 1.2−x}□{sub 0.2}Y{sub x}Ca{sub 1.6}Mn{sub 2}O{sub 7} (x=0.2, 0.3 and 0.4) prepared by a solid state reaction method. The samples crystallize in the tetragonal structure with the space group I4/mmm. Doping with Y decreases the cell parameters and causes a decrease of the metal-insulator transition temperature. The same evolution with doping is also seen for the deduced Curie temperature from susceptibility curves which present a clear paramagnetic-ferromagnetic transition. The significant positive intrinsic magnetoresistance, shown in all samples, reaches 85% at 122 K under 7 T for 0.3 doped sample and can be attributed to the suppression of spin fluctuations via aligning the spins under external magnetic field, while the extrinsic one is attributed to the inter-grain spin-polarized tunneling across the grain boundaries. The simulation of the resistivity curves in the entire temperature range show that the percolation model is suitable to fit our results. The applied magnetic field increases the density of states near the Fermi level, which is in accordance with the observed decrease of resistivity. - Graphical abstract: Resistivity and magnetoresistance of La{sub 1.2−x}□{sub 0.2}Y{sub x}Ca{sub 1.6}Mn{sub 2}O{sub 7} (x=0.2, 0.3, 0.4).more » Solid lines correspond to the fitting results. Display Omitted.« less

Authors:
 [1];  [1];  [2];  [3]; ;  [2]
  1. LEND, Faculty of Science and Technology, Jijel University, Jijel 18000 (Algeria)
  2. Department of Physics, Faculty of Arts and Sciences, AIB University, Bolu 14280 (Turkey)
  3. (KUYTAM), 34450-Sariyer, Istanbul (Turkey)
Publication Date:
OSTI Identifier:
22584171
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 240; Other Information: Copyright (c) 2016 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; CURIE POINT; DENSITY; DENSITY OF STATES; DOPED MATERIALS; FERMI LEVEL; GRAIN BOUNDARIES; MAGNETIC FIELDS; MAGNETIC SUSCEPTIBILITY; MAGNETORESISTANCE; PARAMAGNETISM; PHASE TRANSFORMATIONS; POLYCRYSTALS; SIMULATION; SOLIDS; SPACE GROUPS; SPIN; SPIN ORIENTATION; TETRAGONAL LATTICES; TUNNEL EFFECT; YTTRIUM

Citation Formats

Mahamdioua, N., E-mail: mahamdioua.nabil@gmail.com, Amira, A., Altintas, S.P., Koc University, Surface Science and Technology Center, Varilci, A., and Terzioglu, C.. Structural and magnetotransport properties of the Y doped A-site deficient double layered manganites La{sub 1.2−x}□{sub 0.2}Y{sub x}Ca{sub 1.6}Mn{sub 2}O{sub 7}. United States: N. p., 2016. Web. doi:10.1016/J.JSSC.2016.05.011.
Mahamdioua, N., E-mail: mahamdioua.nabil@gmail.com, Amira, A., Altintas, S.P., Koc University, Surface Science and Technology Center, Varilci, A., & Terzioglu, C.. Structural and magnetotransport properties of the Y doped A-site deficient double layered manganites La{sub 1.2−x}□{sub 0.2}Y{sub x}Ca{sub 1.6}Mn{sub 2}O{sub 7}. United States. doi:10.1016/J.JSSC.2016.05.011.
Mahamdioua, N., E-mail: mahamdioua.nabil@gmail.com, Amira, A., Altintas, S.P., Koc University, Surface Science and Technology Center, Varilci, A., and Terzioglu, C.. Mon . "Structural and magnetotransport properties of the Y doped A-site deficient double layered manganites La{sub 1.2−x}□{sub 0.2}Y{sub x}Ca{sub 1.6}Mn{sub 2}O{sub 7}". United States. doi:10.1016/J.JSSC.2016.05.011.
@article{osti_22584171,
title = {Structural and magnetotransport properties of the Y doped A-site deficient double layered manganites La{sub 1.2−x}□{sub 0.2}Y{sub x}Ca{sub 1.6}Mn{sub 2}O{sub 7}},
author = {Mahamdioua, N., E-mail: mahamdioua.nabil@gmail.com and Amira, A. and Altintas, S.P. and Koc University, Surface Science and Technology Center and Varilci, A. and Terzioglu, C.},
abstractNote = {We present structural, magnetic and electrical properties of the polycrystalline A-site-deficient yttrium doped double layered manganites La{sub 1.2−x}□{sub 0.2}Y{sub x}Ca{sub 1.6}Mn{sub 2}O{sub 7} (x=0.2, 0.3 and 0.4) prepared by a solid state reaction method. The samples crystallize in the tetragonal structure with the space group I4/mmm. Doping with Y decreases the cell parameters and causes a decrease of the metal-insulator transition temperature. The same evolution with doping is also seen for the deduced Curie temperature from susceptibility curves which present a clear paramagnetic-ferromagnetic transition. The significant positive intrinsic magnetoresistance, shown in all samples, reaches 85% at 122 K under 7 T for 0.3 doped sample and can be attributed to the suppression of spin fluctuations via aligning the spins under external magnetic field, while the extrinsic one is attributed to the inter-grain spin-polarized tunneling across the grain boundaries. The simulation of the resistivity curves in the entire temperature range show that the percolation model is suitable to fit our results. The applied magnetic field increases the density of states near the Fermi level, which is in accordance with the observed decrease of resistivity. - Graphical abstract: Resistivity and magnetoresistance of La{sub 1.2−x}□{sub 0.2}Y{sub x}Ca{sub 1.6}Mn{sub 2}O{sub 7} (x=0.2, 0.3, 0.4). Solid lines correspond to the fitting results. Display Omitted.},
doi = {10.1016/J.JSSC.2016.05.011},
journal = {Journal of Solid State Chemistry},
number = ,
volume = 240,
place = {United States},
year = {Mon Aug 15 00:00:00 EDT 2016},
month = {Mon Aug 15 00:00:00 EDT 2016}
}
  • The results of the synthesis and characterization of the optimally doped (La){sub 1.4}(Sr{sub 1-y}Ca{sub y}){sub 1.6}Mn{sub 2}O{sub 7{+-}}{sub {delta}} solid solution with y=0, 0.25, and 0.5 are reported. By progressively replacing the Sr with the smaller Ca, while keeping fixed the hole concentration due to the divalent dopant, the 'size effect' of the cation itself on the structural, transport, and magnetic properties of the bilayered manganite has been analyzed. Two different annealing treatments of the solid solution, in pure oxygen and in pure argon, allowed us to also study the effect of the oxygen content variation. Structure and electronic propertiesmore » of the samples have been investigated by means of x-ray powder diffraction and x-ray absorption spectroscopy measurements. Magnetoresistivity and static magnetization measurements have been carried out to complete the samples characterization. Oxygen annealing of the solid solution, which showed a limit for y{approx}0.5, induces an increase of the Mn average valence state and a transition of the crystal structure from tetragonal to orthorhombic while the argon annealing induces an oxygen understoichiometry and, in turn, a reduction of the Mn average valence state. Along with the Ca substitution, the Jahn-Teller distortion of the MnO{sub 6} octahedra is reduced. This has been directly connected to a general enhancement of the transport properties induced by the Ca doping. For the same cation composition, oxygen overstoichiometry leads to higher metal-insulator transition temperatures and lower resistivity values. Curie temperatures (T{sub C}) are reduced by increasing the Ca doping. The lower T{sub C} for all the annealed samples with respect to the as-prepared ones are connected to the strong influence on the magnetic interactions of the point defects due to the {delta}-variation.« less
  • Samples of La{sub 1-x}Ca{sub x}Mn{sub 1-z}O{sub 3+{delta}} (x = 0.05-0.15) with deficient manganese and excess oxygen {delta} do not pass into a metallic state and have low spin ordering temperatures T{sub C} at acceptor Mn{sup 4+} concentrations near the percolation threshold. These results are explained by carrier localization in clusters near cation vacancies. A break in the carrier transport chain Mn-O-Mn in the form of absent manganese favors cluster formation and decreases the double exchange energy and T{sub C} of the samples. Closeness to the percolation threshold results in strong (more than four orders of magnitude) changes in the electricalmore » resistivity in a magnetic field. The changes in the cluster sizes with the temperature and the magnetic field that are determined from the magnetotransport properties are satisfactorily described in the model of phase separation into small-radius metallic droplets in a dielectric paramagnetic and an antiferromagnetic matrices.« less
  • The influence of {sup 57}Fe-doping and strain effects on the structural and magnetotransport properties of undoped and lightly doped {sup 57}Fe (1 and 3% at Mn site) La{sub 2/3}Ca{sub 1/3}MnO{sub 3} thin films and bulk powder samples have been studied. Thin films were grown on (100)-SrTiO{sub 3} (STO) and (100)-LaAlO{sub 3} (LAO) single crystal substrates, via high O{sub 2} pressure (500 mTorr) using dc magnetron sputtering. Conversion electron Moessbauer (CEM) spectra measured at room temperature in the paramagnetic regime of the Fe-doped samples do not show significant differences in the isomeric shift for the case of the La{sub 2/3}Ca{sub 1/3}MnO{submore » 3} films doped with 1 and 3% iron. The isomeric shift values correspond to the presence of Fe in the 3+ state with octahedral coordination, thus indicating that Fe is incorporated into the structure by substituting Mn. The absence of further states in the spectra indicates that Fe is not involved in forming other additional impurity phases. The x-ray {theta}-2{theta} scan showed that all thin films on LAO and STO have single phase and c-axis strong orientation along the growth direction and the Fe doping gives rise to a relaxation of the epitaxial strain. Finally, we have observed that the saturation magnetization, Curie temperature, metal-insulator transition, and magnetoresistance vary nonmonotonically with increased Fe concentration. This behavior can be understood in terms of competing influences from the strain relaxation, which enhances the tendency to order ferromagnetically, and the reduced double exchange, which is detrimental to the ferromagnetic order.« less
  • No abstract prepared.
  • The transport properties of a single crystal of La{sub 1.2}Ca{sub 1.8}Mn{sub 2}O{sub 7} with the layered Sr{sub 3}Ti{sub 2}O{sub 7}-type perovskite structure have been studied under hydrostatic pressures of up to {approximately}9 kbar. It is found that La{sub 1.2}Ca{sub 1.8}Mn{sub 2}O{sub 7} undergoes a first-order phase transition from a paramagnetic insulating to a low-temperature ferromagnetic metallic state which is accompanied by a large decrease in the electrical resistivity. At ambient pressure the magnetic phase transition takes place at T{sub c}=242 K and as the external pressure is applied the critical temperature increases linearly at a rate of 1.1 K/kbar. Themore » present results reflect the competition between double and superexchange resulting from two-dimensional Mn-O-Mn networks and can be interpreted in terms of the exchange striction model. {copyright} {ital 1997} {ital The American Physical Society}« less