Curie's law

About: Curie's law is a research topic. Over the lifetime, 1164 publications have been published within this topic receiving 21630 citations.

Criterion for Ferromagnetism from Observations of Magnetic Isotherms

Abstract: A criterion is proposed for determining the onset of ferromagnetism in a material as its temperature is lowered from a region in which the linearity of its magnetic moment versus field isotherm gives an indication of paramagnetism. Within the limits of validity of a molecular field treatment, the Curie temperature is shown to be in general indicated by the third power of the magnetization being proportional to the internal magnetic field. The method has been employed to redetermine the Curie point of nickel from the data of Weiss and Forrer, of ${\mathrm{Fe}}_{3}$${\mathrm{O}}_{4}$ from the data of Smith and of some alloys from the data of Kaufmann and his collaborators and the author.

Geometric, electronic, and magnetic structure of Co2FeSi: Curie temperature and magnetic moment measurements and calculations

Abstract: In this work a simple concept was used for a systematic search for materials with high spin polarization It is based on two semiempirical models First, the Slater-Pauling rule was used for estimation of the magnetic moment This model is well supported by electronic structure calculations The second model was found particularly for ${\mathrm{Co}}_{2}$ based Heusler compounds when comparing their magnetic properties It turned out that these compounds exhibit seemingly a linear dependence of the Curie temperature as function of the magnetic moment Stimulated by these models, ${\mathrm{Co}}_{2}\mathrm{FeSi}$ was revisited The compound was investigated in detail concerning its geometrical and magnetic structure by means of x-ray diffraction, x-ray absorption, and M\"ossbauer spectroscopies as well as high and low temperature magnetometry The measurements revealed that it is, currently, the material with the highest magnetic moment $(6{\ensuremath{\mu}}_{B})$ and Curie temperature (1100 K) in the classes of Heusler compounds as well as half-metallic ferromagnets The experimental findings are supported by detailed electronic structure calculations

On the Curie points and high temperature susceptibilities of Heisenberg model ferromagnetics

Abstract: The first six coefficients in the expansion of the susceptibility χ, and its inverse, χ −1, in ascending powers of the reciprocal temperature, have been determined for the Heisenberg model of a ferromagnetic, for any spin value, S, and any lattice. The first five coefficients appropriate to the magnetic specific heat, C, have also been found. For the body-centred and face-centred cubic lattices, the χ and C coefficients are tabulated for half-integral S from 1/2 to 3. From these coefficients estimates have been made of the reduced Curie temperatures, θs c= k T c/J. It is found that for the simple, body-centred and face-centred cubic lattices the formula reproduces the estimated Curie temperatures fairly accurately. Here X=S(S+1) and z is the lattice coordination-number. It is found that, suitably scaled, the theoretical curves for inverse susceptibility against temperature above the Curie point are rather insensitive to the spin value and to the precise lattice structure. The ratio of their initial to the...

Double Hysteresis Loop of BaTi O 3 at the Curie Point

Abstract: It is known that the Curie point $\ensuremath{\theta}$ of the ferroelectric BaTi${\mathrm{O}}_{3}$ shifts to higher temperatures when a dc bias field is applied. If the crystal shows a sharp transition, we expect by applying an ac field at the Curie temperature that the crystal would become alternately ferroelectric and nonferroelectric in the cycle of the ac field. This can be seen in the shape of the hysteresis loop at temperatures slightly above $\ensuremath{\theta}$. In the center of the polarization $P$ versus field $E$ plot, we observe a linear behavior corresponding to the paraelectric state of BaTi${\mathrm{O}}_{3}$ above $\ensuremath{\theta}$. At both high voltage ends, however, we observe a hysteresis loop corresponding to the ferroelectric state. A change in temperature causes a change in size and shape of the double hysteresis loops, ranging from a line with curves at the ends (higher temperature) to two overlapping loops (lower temperature). The results obtained allow us to calculate the different constants in the free-energy expression of Devonshire and Slater. One of the results shows that the transition is of the first order since the ${P}^{4}$ term turns out to be negative. The properties of the hysteresis loops are discussed, especially the large spontaneous electrical polarization and the low coercive field strength.

The Origin of the `Invar' Effect

Abstract: The idea that there are two electronic configurations of iron atoms in a face-centred cubic lattice is extended to the iron-nickel alloy system. With a reasonable variation of the energy difference of these two configurations with nickel concentration it is shown that the `invar' effect originates from the thermal excitation of the configuration with lower atomic volume in opposition to the normal anharmonic origin of expansion. The anomalous pressure dependence of the Curie temperature and the variation of Curie temperature with concentration for alloys containing 30-60% Ni are also shown to follow.