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Curie temperature
About: Curie temperature is a research topic. Over the lifetime, 29206 publications have been published within this topic receiving 584413 citations. The topic is also known as: Curie point.
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TL;DR: In this paper, a new compound composed of Nd, Fe, and a small quantity of B (about 1 wt. %) has been found, which has a tetragonal structure with lattice constants a=0.880 nm and c=1.221 nm.
Abstract: A new compound composed of Nd, Fe, and a small quantity of B (about 1 wt. %) has been found, which has a tetragonal structure with lattice constants a=0.880 nm and c=1.221 nm. This phase, which has the approximate composition, 12 at. % Nd, 6 at. % B and balance Fe, possesses remarkable magnetic properties. From the approach to saturation an anisotroy constant of about 3.5 MJ/m3 can be calculated, while saturation magnetization amounts to 1.35 T. The magnetization versus temperature curve shows a Curie temperature of 585 K, which is much higher than those of the Fe and light rare earth binary compounds. Based on the new compound, sintered permanent magnets have been developed which have a record high energy product. Permanent magnet properties and physical properties of a typical specimen which has the composition Nd15B8Fe77 are as follows: Br =1.23 T, HcB =880 kA/m, HcI =960 kA/m, (BH)max =290 kJ/m3, temperature coefficient of Br =−1260 ppm/K, density=7.4 Mg/m3, specific resistivity=1.4 μΩm, Vickers hardn...
2,525 citations
TL;DR: The discovery of a large magnetic entropy change is reported in MnFeP0.45As0.55, a material that has a Curie temperature of about 300 K and which allows magnetic refrigeration at room temperature, attributed to a field-induced first-order phase transition enhancing the effect of the applied magnetic field.
Abstract: Magnetic refrigeration techniques based on the magnetocaloric effect (MCE) have recently been demonstrated as a promising alternative to conventional vapour-cycle refrigeration1. In a material displaying the MCE, the alignment of randomly oriented magnetic moments by an external magnetic field results in heating. This heat can then be removed from the MCE material to the ambient atmosphere by heat transfer. If the magnetic field is subsequently turned off, the magnetic moments randomize again, which leads to cooling of the material below the ambient temperature. Here we report the discovery of a large magnetic entropy change in MnFeP0.45As0.55, a material that has a Curie temperature of about 300 K and which allows magnetic refrigeration at room temperature. The magnetic entropy changes reach values of 14.5 J K-1 kg-1 and 18 J K-1 kg-1 for field changes of 2 T and 5 T, respectively. The so-called giant-MCE material Gd5Ge2Si2 (ref. 2) displays similar entropy changes, but can only be used below room temperature. The refrigerant capacity of our material is also significantly greater than that of Gd (ref. 3). The large entropy change is attributed to a field-induced first-order phase transition enhancing the effect of the applied magnetic field.
2,272 citations
TL;DR: Thermodynamic analyses show that the magnetoelectric coupling in a nanostructured BaTiO3-CoFe2O4 ferroelectromagnet can be understood on the basis of the strong elastic interactions between the two phases.
Abstract: We report on the coupling between ferroelectric and magnetic order parameters in a nanostructured BaTiO3-CoFe2O4 ferroelectromagnet. This facilitates the interconversion of energies stored in electric and magnetic fields and plays an important role in many devices, including transducers, field sensors, etc. Such nanostructures were deposited on single-crystal SrTiO3 (001) substrates by pulsed laser deposition from a single Ba-Ti-Co-Fe-oxide target. The films are epitaxial in-plane as well as out-of-plane with self-assembled hexagonal arrays of CoFe2O4 nanopillars embedded in a BaTiO3 matrix. The CoFe2O4 nanopillars have uniform size and average spacing of 20 to 30 nanometers. Temperature-dependent magnetic measurements illustrate the coupling between the two order parameters, which is manifested as a change in magnetization at the ferroelectric Curie temperature. Thermodynamic analyses show that the magnetoelectric coupling in such a nanostructure can be understood on the basis of the strong elastic interactions between the two phases.
2,005 citations
TL;DR: In this article, a 3d transition metal-doped ZnO films (n-type Zn1−xMxO) were formed on sapphire substrates using a pulsed-laser deposition technique, and their magnetic and electric properties were examined.
Abstract: 3d-transition-metal-doped ZnO films (n-type Zn1−xMxO (x=005–025): M=Co, Mn, Cr, Ni) are formed on sapphire substrates using a pulsed-laser deposition technique, and their magnetic and electric properties are examined The Co-doped ZnO films showed the maximum solubility limit Some of the Co-doped ZnO films exhibit ferromagnetic behaviors with the Curie temperature higher than room temperature The magnetic properties of Co-doped ZnO films depend on the concentration of Co ions and carriers
1,852 citations
TL;DR: A review of the literature on mixed-valence manganites, placing new results in the context of established knowledge of these materials, and other magnetic semiconductors, is given in this paper.
Abstract: Mixed-valence manganese oxides (R1-χAχ)MnO3 (R=rare-earth cation, A=alkali or alkaline earth cation), with a structure similar to that of perovskite CaTiO3, exhibit a rich variety of crystallographic, electronic and magnetic phases. Historically they led to the formulation of new physical concepts such as double exchange and the Jahn-Teller polaron. More recent work on thin films has revealed new phenomena, including colossal magnetoresistance near the Curie temperature, dense granular magnetoresistance and optically-induced magnetic phase transitions. This review gives an account of the literature on mixed-valence manganites, placing new results in the context of established knowledge of these materials, and other magnetic semiconductors. Issues addressed include the nature of the electronic ground states, the metal-insulator transition as a function of temperature, pressure and applied magnetic field, the electronic transport mechanisms, dielectric and magnetic polaron formation, magnetic localization, ...
1,757 citations