Crystal Structures, Magnetic and Electrical Properties of Manganese Perovskites

2008 ◽  
Vol 59 (11) ◽  
Author(s):  
Emil Burzo ◽  
Istvan Balasz ◽  
Mihaela Albu
Keyword(s):  
Electrical Properties ◽  
Valence State ◽  
Oxygen Vacancies ◽  
Magnetic Ordering ◽  
Double Exchange ◽  
Charge Compensation ◽  
Rhombohedral Structure ◽  
Compensation Mechanism ◽  
Dominant Mechanism ◽  
Al Content

The Y0.67Ca0.33Mn1-yAlyO3 system with y � 0.2, crystallizes in an orthorhombic type structure having Pnma space group. The La1-xPbxMnO3 perovskites with 0.24 � x 0.40 have a rhombohedral structure of R 3c�type. The Y0.67Ca0.33Mn1-yAlyO3 samples show a mictomagnetic type behaviour. The analysis of charge compensation mechanism suggests that the number of oxygen vacancies increases with Al content. A semiconducting type behaviour was also shown. The contributions of double exchange mechanism to magnetic ordering in La1-xPbxMnO3 increase as the lead content is higher. A nearly ferromagnetic type ordering was shown for the sample with x=0.4. The number of Mn4+ ions fits well with the Pb2+ ones, suggesting that the change in Mn valence state is the dominant mechanism for charge compensation. A transition from metallic to semiconducting type behaviour is shown at temperatures by@130 K lower than the Curie points. Magnetoresistivities up to @ 50 % were determined in fields of 60�70 kOe.

Magnetic Ordering via Itinerant Ferromagnetism in a Metal-Organic Framework

2020 ◽  
Author(s):  
Jesse Park ◽  
Brianna Collins ◽  
Lucy Darago ◽  
Tomce Runcevski ◽  
Michael Aubrey ◽  
...  
Keyword(s):  
Charge Transport ◽  
Magnetic Order ◽  
Metal Organic Framework ◽  
Metal Organic Frameworks ◽  
Magnetic Ordering ◽  
Double Exchange ◽  
Itinerant Ferromagnetism ◽  
Organic Solids ◽  
Metal Organic ◽  
Organic Framework

<b>Materials that combine magnetic order with other desirable physical attributes offer to revolutionize our energy landscape. Indeed, such materials could find transformative applications in spintronics, quantum sensing, low-density magnets, and gas separations. As a result, efforts to design multifunctional magnetic materials have recently moved beyond traditional solid-state materials to metal–organic solids. Among these, metal–organic frameworks in particular bear structures that offer intrinsic porosity, vast chemical and structural programmability, and tunability of electronic properties. Nevertheless, magnetic order within metal–organic frameworks has generally been limited to low temperatures, owing largely to challenges in creating strong magnetic exchange in extended metal–organic solids. Here, we employ the phenomenon of itinerant ferromagnetism to realize magnetic ordering at <i>T</i><sub>C</sub> = 225 K in a mixed-valence chromium(II/III) triazolate compound, representing the highest ferromagnetic ordering temperature yet observed in a metal–organic framework. The itinerant ferromagnetism is shown to proceed via a double-exchange mechanism, the first such observation in any metal–organic material. Critically, this mechanism results in variable-temperature conductivity with barrierless charge transport below <i>T</i><sub>C</sub> and a large negative magnetoresistance of 23% at 5 K. These observations suggest applications for double-exchange-based coordination solids in the emergent fields of magnetoelectrics and spintronics. Taken together, the insights gleaned from these results are expected to provide a blueprint for the design and synthesis of porous materials with synergistic high-temperature magnetic and charge transport properties. </b>

scholarly journals Structural, Optical and Electrical Properties of Al+MoO3 and Au+MoO3 Thin Films Prepared by Magnetron Codeposition

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 766
Author(s):  
Tihomir Car ◽  
Ivan Jakovac ◽  
Ivana Šarić ◽  
Sigrid Bernstorff ◽  
Maja Micetic
Keyword(s):  
Thin Films ◽  
Electrical Properties ◽  
Au Nanoparticle ◽  
Content Increase ◽  
Optical And Electrical Properties ◽  
Volume Percentage ◽  
Sputtering Deposition ◽  
Nanoparticle Formation ◽  
Al Content ◽  
Sputtering Power

Structural, optical and electrical properties of Al+MoO3 and Au+MoO3 thin films prepared by simultaneous magnetron sputtering deposition were investigated. The influence of MoO3 sputtering power on the Al and Au nanoparticle formation and spatial distribution was explored. We demonstrated the formation of spatially arranged Au nanoparticles in the MoO3 matrix, while Al incorporates in the MoO3 matrix without nanoparticle formation. The dependence of the Au nanoparticle size and arrangement on the MoO3 sputtering power was established. The Al-based films show a decrease of overall absorption with an Al content increase, while the Au-based films have the opposite trend. The transport properties of the investigated films also are completely different. The resistivity of the Al-based films increases with the Al content, while it decreases with the Au content increase. The reason is a different transport mechanism that occurs in the films due to their different structural properties. The choice of the incorporated material (Al or Au) and its volume percentage in the MoO3 matrix enables the design of materials with desirable optical and electrical characteristics for a variety of applications.

scholarly journals Effects of Charge Compensation on Colossal Permittivity and Electrical Properties of Grain Boundary of CaCu3Ti4O12 Ceramics Substituted by Al3+ and Ta5+/Nb5+

Molecules ◽  
2021 ◽  
Vol 26 (11) ◽  
pp. 3294
Author(s):  
Jakkree Boonlakhorn ◽  
Jedsada Manyam ◽  
Pornjuk Srepusharawoot ◽  
Sriprajak Krongsuk ◽  
Prasit Thongbai
Keyword(s):  
Dielectric Properties ◽  
Electrical Properties ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Barrier Height ◽  
Potential Barrier ◽  
Charge Compensation ◽  
Solid State Reaction Method ◽  
Wide Frequency Range ◽  
Potential Barrier Height

The effects of charge compensation on dielectric and electrical properties of CaCu3Ti4-x(Al1/2Ta1/4Nb1/4)xO12 ceramics (x = 0−0.05) prepared by a solid-state reaction method were studied based on the configuration of defect dipoles. A single phase of CaCu3Ti4O12 was observed in all ceramics with a slight change in lattice parameters. The mean grain size of CaCu3Ti4-x(Al1/2Ta1/4Nb1/4)xO12 ceramics was slightly smaller than that of the undoped ceramic. The dielectric loss tangent can be reduced by a factor of 13 (tanδ ~0.017), while the dielectric permittivity was higher than 104 over a wide frequency range. Impedance spectroscopy showed that the significant decrease in tanδ was attributed to the highly increased resistance of the grain boundary by two orders of magnitude. The DFT calculation showed that the preferential sites of Al and Nb/Ta were closed together in the Ti sites, forming self-charge compensation, and resulting in the enhanced potential barrier height at the grain boundary. Therefore, the improved dielectric properties of CaCu3Ti4-x(Al1/2Ta1/4Nb1/4)xO12 ceramics associated with the enhanced electrical properties of grain boundaries. In addition, the non-Ohmic properties were also improved. Characterization of the grain boundaries under a DC bias showed the reduction of potential barrier height at the grain boundary. The overall results indicated that the origin of the colossal dielectric properties was caused by the internal barrier layer capacitor structure, in which the Schottky barriers at the grain boundaries were formed.

scholarly journals The Peter Day Series of Magnetic (Super)Conductors

2021 ◽  
Vol 7 (7) ◽  
pp. 93
Author(s):  
Samia Benmansour ◽  
Carlos J. Gómez-García
Keyword(s):  
Magnetic Properties ◽  
Electrical Properties ◽  
Metal Complexes ◽  
Long Range ◽  
Magnetic Ordering ◽  
Metallic Conductivity ◽  
Electrical And Magnetic Properties ◽  
Super Conducting ◽  
Paramagnetic Metals

Here, we review the different series of (super)conducting and magnetic radical salts prepared with organic donors of the tetrathiafulvalene (TTF) family and oxalato-based metal complexes (ox = oxalate = C2O42−). Although most of these radical salts have been prepared with the donor bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF = ET), we also include all the salts prepared with other TTF-type donors such as tetrathiafulvalene (TTF), tetramethyl-tetrathiafulvalene (TM-TTF), bis(ethylenediseleno)tetrathiafulvalene (BEST), bis(ethylenedithio)tetraselenafulvalene (BETS) and 4,5bis((2S)-2-hydroxypropylthio)-4’,5’-(ethylenedithio)tetrathiafulvalene (DMPET). Most of the oxalate-based complexes are monomers of the type [MIII(C2O4)3]3−, [Ge(C2O4)3]2− or [Cu(C2O4)2]2−, but we also include the reported salts with [Fe2(C2O4)5]4− dimers, [MII(H2O)2[MIII(C2O4)3]2]4− trimers and homo- or heterometallic extended 2D layers such as [MIIMIII(C2O4)3]− and [MII2(C2O4)3]2−. We will present the different structural families and their magnetic properties (such as diamagnetism, paramagnetism, antiferromagnetism, ferromagnetism and even long-range magnetic ordering) that coexist with interesting electrical properties (such as semiconductivity, metallic conductivity and even superconductivity). We will focus on the electrical and magnetic properties of the so-called Day series formulated as β”-(BEDT-TTF)4[A+MIII(C2O4)3]·G, which represents the largest family of paramagnetic metals and superconductors reported to date, with more than fifty reported examples.

Novel Magnetic Orders and Ice Phases in Frustrated Kondo-Lattice Models

SPIN ◽  
2015 ◽  
Vol 05 (02) ◽  
pp. 1540006 ◽  
Author(s):  
Gia-Wei Chern
Keyword(s):  
Berry Phase ◽  
Magnetic Moments ◽  
Lattice Models ◽  
Magnetic Ordering ◽  
Double Exchange ◽  
Salient Feature ◽  
Kondo Lattice ◽  
Spin Ice ◽  
Water Ice ◽  
Ising Magnets

We review recent theoretical progress in our understanding of electron-driven novel magnetic phases on frustrated lattices. Our specific focus is on Kondo-lattice or double-exchange models assuming finite magnetic moments localized at the lattice sites. A salient feature of systems with SU(2) symmetric local moments is the emergence of noncoplanar magnetic ordering driven by the conduction electrons. The complex spin textures then endow the electrons a nontrivial Berry phase, often giving rise to a topologically nontrivial electronic state. The second part of the review is devoted to the discussion of metallic spin ice systems, which are essentially frustrated Ising magnets with local spin ordering governed by the so-called ice rules. These rules are similar to those that describe proton configurations in solid water ice, hence the name "spin ice". The nontrivial spin correlations in the ice phase give rise to unusual electron transport properties in metallic spin-ice systems.

scholarly journals A new approach to improve the electrochemical performance of ZnMn2O4 through a charge compensation mechanism using the substitution of Al3+ for Zn2+

RSC Advances ◽  
2018 ◽  
Vol 8 (14) ◽  
pp. 7361-7368
Author(s):  
Xianyu Zhu ◽  
Jingbin Quan ◽  
Jichun Huang ◽  
Zheng Ma ◽  
Yixin Chen ◽  
...  
Keyword(s):  
Electrochemical Performance ◽  
Charge Compensation ◽  
Compensation Mechanism ◽  
New Approach ◽  
A Charge

This work reports the nonequivalent substitution of ZnMn2O4. This is a new approach to improve the electrochemical performance of ZnMn2O4 through a charge compensation mechanism using the substitution of Al3+ for Zn2+.

Effect of TiO2 Nanoparticle on the Structural and Electrical Properties of Nd0.67Sr0.33MnO3 /TiO2 Composites

2021 ◽  
Vol 317 ◽  
pp. 60-65
Author(s):  
Kean Pah Lim ◽  
Lik Nguong Lau ◽  
Amirah Natasha Ishak ◽  
Mohd Mustafa Awang Kechik ◽  
Soo Kien Chen ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Grain Boundary ◽  
Double Exchange ◽  
Secondary Phase ◽  
Solid State Reaction Method ◽  
Peak Shift ◽  
Boundary Region ◽  
Structural And Electrical Properties ◽  
Xrd Patterns ◽  
Grain Surface

In this work, (1-x) (Nd0.67Sr0.33MnO3): x (TiO2) composites with x = 0, 0.1, 0.2, 0.3 and 0.4 have been prepared to investigate the structural and electrical properties. Nd0.67Sr0.33MnO3 (NSMO) was synthesised via the solid-state reaction method before incorporated with TiO2. The addition of TiO2 nanoparticle as the secondary phase in manganite composite would favour the spin-polarized tunnelling near to the grain boundary and thus enhance the extrinsic magnetoresistance. Nevertheless, nanoparticle addition might contribute to substitution and diffusion with manganite compound as reported in literature. The effect of the TiO2 nanoparticle addition into NSMO composites has been examined by an X-ray diffractometer (XRD) and a four-point probe (4PP) system. From the thermogravimetric analysis (TGA), NSMO phase formation occurred in between 756.45 - 977.59 °C. XRD patterns showed that there is no peak shift when the TiO2 concentration increases. It can be deduced that TiO2 was segregated at the NSMO grain boundary region and its grain surface. However, a small amount of Ti atoms are expected to replace the Mn atoms in NSMO crystal system and has caused the increase in crystallite size. The electrical study showed that the presence of TiO2 nanoparticle and substitution of Ti in Mn sites have weaken the double exchange (DE) mechanism and suppressed the metal-insulator transition temperature (TMI). In addition, the insulating behaviour of TiO2 has also caused the resistivity of composites to increase drastically.

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