Electrical transport properties and magnetic cluster glass behavior of Nd0.7Sr0.3MnO3 nanoparticles
TL;DR: In this article, the transport and magnetic properties of Nd07Sr03MnO3 nanoparticles were investigated by the sol-gel method and the results showed that resistivity increases with the decrease of the particle size due to the enhancement of the grain boundary effect.
Abstract: The transport and magnetic properties have been investigated in Nd07Sr03MnO3 nanoparticles prepared by the sol-gel method The resistivity (ρ) increases with the decrease of the particle size due to the enhancement of the grain boundary effect ρ(T) shows two distinct transitions for all the samples such as metal-insulator transition and transition due to the barrier caused by the grain boundary effect The thermopower (S) is found to be negative and at high temperature S follows the adiabatic small polaron hopping theory In the metallic region the spin wave contribution is found to be dominant in the temperature dependence of the thermopower The magnetoresistance (MR) of the ultrafine particles increases with the decrease of particle size indicating substantial contribution from the grain boundaries Spin polarized intergrain tunneling effect plays an important role in the MR of a smaller size particle, whereas in the case of samples of higher dimension spin fluctuation contributes predominantly The
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TL;DR: In this paper, the temperature dependence of the ac magnetic susceptibility was measured at different frequencies and ac magnetic fields in the selected ranges of 40-1000-Hz and 80-800-A/m, respectively.
96 citations
TL;DR: In this article, the magnetic properties of compacted La0.8Ca0.2MnO3 manganite nanoparticles with average particle size of 18 and 70 nm and Curie temperatures TC 231 K and TC 261 K, respectively, have been investigated.
Abstract: Magnetic properties of compacted La0.8Ca0.2MnO3 manganite nanoparticles with average particle size of 18 and 70 nm and Curie temperatures TC 231 K and TC 261 K, respectively, have been investigated. The relative volume of the ferromagnetic phase has been estimated to be 52% for ensembles of 18 nm particles and 92% for 70 nm particles. It was found that applied hydrostatic pressure enhances TC of La0.8Ca0.2MnO3 nanoparticles at a rate dTC /dP 1.8– 1.9 K / kbar, independently on the average particle size. Pronounced irreversibility of magnetization below Tirr 208 K and strong frequency dependent ac susceptibility below TC for smaller 18 nm particles have been observed. 18 nm particles have also shown aging and memory effects in zero-field-cooled ZFC and field-cooled magnetization. These features indicate the appearance of spin-glasslike state, partially reminiscent the behavior of La1�xCaxMnO3 crystals, doped below the percolation threshold xxC = 0.225. In contrast, ensembles of larger 70 nm particles have shown insignificant irreversibility of magnetization only and no frequency dependence of ac susceptibility, similarly to the behavior of La1�xCaxMnO3 crystals with xxC. The temperature of the ZFC magnetization maximum for 18 nm particles decreases with increasing magnetic field and forms a critical line with an exponent 1.89 0.56. The results suggest that superspin-glass features in ensembles of interacting 18 nm particles appear along with superferromagnetic-like features.
86 citations
TL;DR: In this article, structural, magnetic, and electrical properties of the La0.8−xSmxSr0.2MnO3 manganites prepared by a solid-state reaction technique was studied systematically.
58 citations
TL;DR: In this article, the authors systematically outline some fundamentals and key experimental results concerning magnetic properties of perovskite manganites, focusing on magnetocaloric properties, pressure effect on magnetic properties, and magnetism of manganite nanoparticles.
Abstract: This chapter attempts to systematically outline some fundamentals and key experimental results concerning magnetic properties of perovskite manganites, focusing on (i) magnetocaloric properties, (ii) pressure effect on magnetic properties, and (iii) magnetism of manganite nanoparticles. Each family of manganites has unique properties that can be used as a way of tuning the optimum magnetocaloric response. The relatively easy possibility of tuning the Curie temperature of manganites is a key point in developing efficient magnetocaloric materials. The most interesting effects of applied external pressure observed for various classes of manganite systems, such as hole-doped manganites; parent, single-valent, and self-doped manganites; hexagonal manganites, near-half-doped manganites, electron-doped manganites, and manganite nanoparticles are reviewed. Some of the most relevant finite-size and surface effects on the magnetic properties of ferromagnetic and antiferromagnetic manganite nanoparticles are also discussed. New phenomena such as a suppression of charge/orbital ordering with decreasing particle size, collective states, and nonequilibrium dynamics in ensembles of antiferromagnetic manganite nanoparticles are presented.
57 citations
TL;DR: In this article, the authors determined the values of critical exponents of two polycrystalline samples (Nd1−xYx)0.7Sr0.3MnO3 (x = 0 and 0.07) from the magnetization data versus temperature and magnetic field, M(H, T), to learn about their magnetic and magnetocaloric (MC) properties.
44 citations
References
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13 May 1993
TL;DR: The phase of condensed matter known as spin glasses has become a vital and productive area of research as mentioned in this paper, and experiment has suggested unusual effects which have brought the theoretical study of the spin glass Problem Onto The Same Footing As The Experimental Study.
Abstract: The phase of condensed matter known as spin glasses has become a vital and productive area of research. Historically, experiment has suggested unusual effects which have brought the theoretical study of the spin Glass Problem Onto The Same Footing As The Experimental Study. Experiments in the late 1960s on magnetic alloys presented interesting effe
1,746 citations
TL;DR: In this paper, the magnetoresistance and the field dependent magnetization have been systematically examined in the low temperature ferromagnetic metallic state of single crystal and polycrystalline.
Abstract: The magnetoresistance (MR) and the field dependent magnetization have been systematically examined in the low temperature ferromagnetic metallic state of single crystal and polycrystalline ${\mathrm{La}}_{2/3}{\mathrm{Sr}}_{1/3}{\mathrm{MnO}}_{3}$. We find that the intrinsic negative MR in single crystal is due to the suppression of spin fluctuations, and magnetic domain boundaries do not dominate the scattering process. In contrast, we demonstrate that the MR in the polycrystalline samples exhibits two distinct regions: large MR at low fields dominated by spin-polarized tunneling between grains and high field MR which is remarkably temperature independent from 5 to 280 K.
1,594 citations
TL;DR: In this paper, a classification of nanostructure morphology according to the mechanism responsible for the magnetic properties is presented, followed by a brief discussion of some promising experimental techniques in synthesis and measurements.
Abstract: Understanding the correlation between magnetic properties and nanostructure involves collaborative efforts between chemists, physicists, and materials scientists to study both fundamental properties and potential applications. This article introduces a classification of nanostructure morphology according to the mechanism responsible for the magnetic properties. The fundamental magnetic properties of interest and the theoretical frameworks developed to model these properties are summarized. Common chemical and physical techniques for the fabrication of magnetic nanostructures are surveyed, followed by some examples of recent investigations of magnetic systems with structure on the nanometer scale. The article concludes with a brief discussion of some promising experimental techniques in synthesis and measurements.
1,522 citations
Book•
26 Nov 1999
TL;DR: The classical and quantum properties of magnetism have been discussed in this article, including magnetization, magnetization in small structures, exchange couplings and nanocrystals, and magnetic recording.
Abstract: Introduction and Overview. Magnetostatics. Classical and Quantum Phenomenology of Magnetism. Quantum Mechanics, Magnetism, and Exchange in Atoms and Oxides. Quantum Mechanics, Magnetism, and Bonding in Metals. Magnetic Anisotropy. Magnetoelastic Effects. Magnetic Domain Walls and Domains. Magnetization Process. Soft Magnetic Materials. Amorphous Materials: Magnetism and Disorder. Magnetism in Small Structures: Exchange Coupling and Nanocrystals. Hard Magnetic Materials. Magnetic Annealing and Directional Order. Electronic Transport in Magnetic Materials. Surface and Thin-Film Magnetism. Magnetic Recording. Appendices. Index.
1,425 citations