Magnetic phase transition temperature

By increasing the sample temperature both peaks of the Tb(OOOl) surface state shift towards thereby decreasing the exchange splitting A ex- Just above Tcb (T — 223 K) the occupied part of the surface state has already approached the Fermi level very closely [U — —50 34 mV]. In contrast to earlier experiments on Gd(OOOl), this trend continues for Tb(OOOl) even above its bulk magnetic phase transition temperatures Tcb = 220 K and Tnb = 228 K. At T = 248 K the former occupied part of the surface state is energetically localized at the Fermi level [17 = 10 30 mV]. Increasing the temperature further T — 258 K and T — 271 K) the maximum in the dUdU spectra crosses Ejs. As a result the surface state which was clearly occupied at low temperature (T = 85 K) becomes partially empty above T = 250 K. 

Magnetic phase transitions (temperature region 2 TxTj, Tq, %)... 

Fig. 6.7. Mossbauer parameters for Fe in DyFe as a function of temperature, showing the decrease in the recoil-free fraction at the magnetic phase transition temperature 7i . (Feder Nowik, 1979.)...

FIGURE 54 Linear thermal expansion of CeRh Sij at low temperature at various pressures. The arrows indicate the magnetic phase transition temperatures, Tm and Tn2 (Honda et al., 1999). 

Many authors have contributed to the study of die shift of magnetic phase transition temperatures under pressure in the heavy lanthanides and their alloys - see tables 1-3... 

Magnetic phase transition temperatures and their pressure dependence in gadolinium... 

For example, 0 describes the temperature dependence of composition near the upper critical solution temperature for binary (liquid + liquid) equilibrium, of the susceptibility in some magnetic phase transitions, and of the order parameter in (order + disorder) phase transitions. 

At lower temperatures, the standard 3D helical order with all chains having not only the same chirality but also the same phase can be established. The two magnetic phase transitions present very different features. In fact, the transition to the... 

Fig. 33. Temperature dependence of the susceptibility of GdNi2B2C measured at 1 Tesla on an oriented powder, indicating the two magnetic phase transitions near 20 K and 14 K (after Felner 2001).

Few of the many known ferromagnetic solids are suitable as catalysts for the nondissociative ortho-parahydrogen conversion. This is especially true if measurements are needed in the neighborhood of the magnetic phase transition, Tc. The reasons for this are threefold the solid may decompose at the temperature necessary to free the surface from contaminants, the Curie point may be so low that the experimental difficulties are formidable, and many such solids show strong dissociative conversion activity near Tc. Of the three solids named above none is very satisfactory. 

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