Ordered magnets

To further clarify the role of magnetic effects on compressibility, a shock compression experiment was performed on an fee 28.5-at. % Ni sample whose initial temperature was raised to 130°C. As is shown in Table 5.1, the compressibility was found to decrease to a value consistent with the nonmagnetic compressibility. Thus, the sharp change in compressibility, the critical values for the transition, and the magnitudes of the compressibility under the various conditions give a clear demonstration that a second-order magnetic transition has been observed, and we will proceed with a quantitative analysis of the transition. 

Fig. 34—Bit pattern media (BPM) or self-ordered magnetic arrays.

Lelievre-Bema, E., Rouchy, J. and Ballou, R. (1994) Field induced first order magnetic transition and associated volume effect in TbMn2, J. Mag. Mag. Mar., 137, L6-L10. 

The Inden model [20] is frequently used to describe second-order magnetic order-disorder transitions. Inden assumed that the heat capacity varied as a logarithmic function of temperature and used separate expressions above and below the magnetic order-disorder transition temperature (TtIS) in order to treat the effects of both long- and short-range order. Thus for z = (T/TtIS) < 1 ... 

Energy transfer probabilities due to multipolar magnetic interactions also behave in a similar way to that previously discussed for multipolar electric interactions. Thus, the transfer probability for a magnetic dipole-dipole interaction also varies with 1 / 7 , and higher order magnetic interactions are only influential at short distances. In any case, the multipolar magnetic interactions are always much less important than the electric ones. 

The definitions of the first and second order magnetic perturbation operators are given helow. In the nonrelativistic formalism these operators are two-component operators, in the Kutzelnigg formalism all operators are to he multiplied hy the four-component matrix. All operators are given in the atomic unit system and we do not apply QED corrections so that the free electron g-factor is precisely equal to 2. 

We then turn to the question of how to eliminate the spin-orbit interaction in four-component relativistic calculations. This allows the assessment of spin-orbit effects on molecular properties within the framework of a single theory. In a previous publication [13], we have shown how the spin-orbit interaction can be eliminated in four-component relativistic calculations of spectroscopic properties by deleting the quaternion imaginary parts of matrix representations of the quaternion modified Dirac equation. We show in this chapter how the application of the same procedure to second-order electric properties takes out spin-forbidden transitions in the spectrum of the mercury atom. Second-order magnetic properties require more care since the straightforward application of the above procedure will extinguish all spin interactions. After careful analysis on how to proceed we... 

The closest Er—Er distance is 11.7 A thus providing the ordered, magnetically dilute erbium ion with a local symmetry of On-... 

Mossbauer spectra are used for identification and and characterization of Fe oxi-des.This follows primarily from the fact that the different Fe oxides order magnetically over a wide range of temperatures from 950 down to below 78K. The Mossbauer parameters of the various magnetically ordered Fe oxides differ considerably and thus allow unequivocal identification and often quantification in mixtures to be made. Mossbauer spectroscopy is insensitive to all isotopes except Fe (and a few... 

We illustrate the CVD preparation of thin films with some examples. The selected materials are ferromagnetic [Fe+ (Cp )2][TCNE] and the solvent-free V(TCNE) c phase. [Ee+ (Cp )2][TCNE] is a ferromagnet with Tq = 4.8 K (Miller etal, 1988) and V[TCNE] c orders magnetically above 350 K (Manriquez et al., 1991), as previously discussed in Section 1.5. Table 3.2 summarizes the CVD conditions for growth of the thin films. V(TCNE) c and [Fe+ (Cp )2][TCNE] correspond to type I and II, respectively. 

A good example is given by intermetallic compounds with the AuCus crystal structure the interactinide spacing are very large (4 A or over) and they should all be magnetic whereas less than half of the compounds studied thus far order magnetically. 

Table 9. Conduction electron polarization effect in uranium ferromagnetic monocompounds conduction electron polarization moment Psai saturation moment from magnetization studies ordered magnetic moment as determined by neutron scattering...

The symbol P means that the compound follows a C.W. (Curie-Weiss) (or M.C.W.) law, but doesn t order magnetically. 

In UPts, a compound for which spin-fluctuations are known to exist, superconduction has recently been reported There is an apparent contradiction with the classical Bar-deen-Cooper model for superconductivity, in which superconduction is hindered by the onset of ordered magnetic phenomena, and is usually not found in very narrow bands. UBei3 which has a y of 1000 mg/mol K, exhibits similar behaviour. 

Tinkham, M., 1970a. Far infrared absorption in ordered magnetic systems, in Far-Infrared Properties of Solids, S. S. Mitra, and S. Nudelman (Eds.), Plenum, New York, pp. 196-222. 

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