Anti-Curie temperature

The exchange energy coefficient M characterizes the energy associated with the (anti)paraHel coupling of the ionic moments. It is direcdy proportional to the Curie temperature T (70). Experimental values have been derived from domain-width observations (69). Also the temperature dependence has been determined. It appears thatM is rather stable up to about 300°C. Because the Curie temperatures and the unit cell dimensions are rather similar, about the same values forM may be expected for BaM and SrM. 

Values relative to the cysteines whose signals have an anti-Curie-type temperature dependence. 

Note that we have a structure with a "built-in crystal defect, a vacancy. Both the lithium and niobium cations are in an octahedral coordination. In fact, the two ions, Li and Nb , have nearly the same radius and occupy octahedral sites with the same Cgy S5mimetry. The lithium deficiency in congruent crystals is accommodated by means of Nb anti-sites and Nb vacancies in a relative concentration that guaranties overall electrical neutrality. Note that many physical properties depend upon stoichiometry, e.g.- Curie temperature, absorption spectra, lattice parameters and photorefractive yield. 

Fig. S. Qualitative schematic representation of the temperature dependence with spin magnetization (Si) for the two local or intermediate spin states Sa and Sb, which couple to yield a total cluster spin state St- The qualitative behavior shown is that for SaI > I B. The three regions are (1) high temperature limit, where both Si)a and (Sj)b exhibit Curie-like behavior with the same sign, (2) intermediate temperature where S )a exhibits Curie-like and S )b anti-Curie behavior, both with the same sign, and (3) low temperature limit where S )a exhibits Curie-like behavior and (5j)b exhibits Curielike behavior but with opposite signs from that of (Sj)a. The observed behavior for both 3Fe Fd and 4Fe Fd" is that shown for region (2). [Reprinted from S. C. Busse, G. N. La Mar, L. P. Yu, J. B, Howard, E. T. Smith, Z. H. 2ihou, and M. W. W. Adams, Biochemistry 31,11952 (1992), with permission.]...

Fig. 15. Plot of chemical shift vs reciprocal absolute temperature (Curie plot) of the resolved CpH, Cp H, and CaH peaks for Cys A [Cys-17(III)], B [Cys-56(IV)], and C [Cys-11(1)] for /ySFe Fd° at pH 8.0 (solid markers, solid lines) and at pH 3.4 (open markers, dashed lines) in H20 at 30°. Note that while Cys A and B exhibit anti-Curie (negative slope) and Cys C display Curie-like (positive slope) behavior at pH 8.0, all three Cys exhibit similarly weak anti-Curie bdiavior at low pH. [Reprinted from C. M. Goist, Y.-H. Yeh, Q. Teng, L. Calzolai, Z-H. Zhou, M. W. W. Adams, and G. N. La Mar, Biochemistry 34,600 (1995), with permission.]...

Effect ofNon-Cys Ligands. Pf Fd is unique in providing a very stable protein for which the ligation of Asp-14(II) in WT and a Sct in the D14S-Fd could be unequivocally demonstrated in both presence (Fd ) and absence (Fd ) of the disulfide bond. The conserved oxidation-state equivalent environments of the four iron is supported by the observation of Cys CpH 8fcon and variable temperature behavior (uniformly anti-Curie) that are conserved relative to all Cys-ligated... 

The equivalence between Eq. (15) and Eq. (9) allows us to evaluate the Qj coefficients and accounts for their physical meaning they indicate how much Sj and Msj are contributing to each S) wavefunction of the couple. Equation (16) is easily applicable in all cases. As a practical example of use of Eq. (16) Appendix II shows the numerical calculation of the high temperature limit. It can be noted that the temperature dependence of the isotropic shifts is often opposite to that observed in monomeric complexes (anti-Curie behavior). In principle, fitting of experimental temperature dependent data to Eq. (16) can give a measure of J. Attempts to estimate J from temperature dependence were previously reported in a number of cases [4,13,19] however, equations of the type of (11) were used, with... 

Within single crystals and ceramic crystallites, respectively, the dipole moments of neighbouring domains are either perpendicular or anti-parallel to each other. For polycrystalline materials the orientation of the crystallites and thus of the domains is randomly distributed. In the original state these materials do not exhibit a macroscopic polarization and thus no piezoelectric effect. However, the latter can be induced by applying a static electric field below the Curie temperature where the domains of uniform dipole moments arrange towards the polarization field (paraelectric polarization). The field strength applied should be between the saturation and the breakdown range. Due to this polarization the ferroelectric material becomes piezoelectric. 

CACT. Center for Advanced Ceramic Technology, at Alfred University, USA. CAD/CAM. Computer Aided Design/ Computer Aided Manufacture Cadmium Carbonate. CdC03. Small amounts (up to 2%) are sometimes added to cadmium selenide (q.v.) red colours to improve their stability. Cadmium Niobate. Cd2Nb207 an anti-ferroelectric compound the Curie temperature lies between - 85°C and -100 °C. 

A plot of tlie reciprocal of the measured susceptibility 1 /Zmoi vs. r is a straight line with slope 1/C, and which crosses the abscissa at T = 0 (Fig. 19.6). For 0 = 0 the equation is simplified to the classic Curie law = C/T. Generally, values of 0 0 are found when cooperative effects arise at low temperatures (ferro-, ferri- or anti ferromagnetism). The straight line then has to be extrapolated from high to low temperatures (dashed lines in Fig. 19.6). 

The compound with pentacyanopropenide was found to possess a ID-DAD A structure in the solid state, but the main magnetic behavior was of the anti-ferromagnetic type, as the material obeys the Curie-Weiss law (7 = C/T — 6) governing the temperature dependence of the magnetic susceptibility with 6 = —1.2 K (compare with 6 = -1-30 K for [FeCpf] [TCNE], above 60 K) [28]. 

CeMnSna and 7 c = 520K for CeMno.sSna- The xiT) dependence of the Ce compounds follow the Curie-Weiss law above the Tq points, and the xiT) dependences of the LaMni 2(Sn2 y, PrMni jSna-, NdMni-j Sna-, and SmMni Sna- - compounds obey the Curie-Weiss law above the liquid nitrogen temperature. The Pr, Nd and Sm compounds undergo an anti ferromagnetic phase transition at low temperatures. 

---