Europium magnetic transition

The heat capacity of the semiconducting orthorhombic europium hydride was measured by Drulis and Stalinski (1989) for EuHi.gs and by Drulis (1993) for EuD2, who observed a L-type anomaly for the magnetic transition at Tc=15.8K for the former and at Tc = 16.3 K for the latter (see sect. 6). The T-dependence of Cp above 50K exhibits a marked isotope effect which was analysed by Drulis (1993) on the basis of hydrogen optical modes as determined from infrared absorption spectra. 

Lux et al. (1991a) examined the compounds Eui jGdxPtP and Euo.sSro sPtP which have the same structures as a- or P-EuPtP, but do not undergo first-order phase transitions at x>0.05. Their Lm-X-ray absorption and magnetic susceptibility studies have shown a dependence similar to that of EuPtP, but only one magnetic transition was foimd. The temperatures of antiferromagnetic order in these compounds depend on europium content and have the following values 7.5 K (5% Gd), 6.8 K (10% Gd) and 6.4 K (50% Sr). 

Although there always seemed to be theoretical unanimity on the existence of magnetochiral anisotropy, it was not observed experimentally until a few years ago. The most strongly chiral optical transitions reported in the literature are the 5D0 —> 7 Fij2 luminescent transitions in tris(3-trifluoroacetyl- -camphorato) europium(III) complexes (Eu(( )tfc)3). These transitions also have a considerable MCD. Such complexes are therefore likely candidates to show a significant magnetochiral effect. The experiment performed by us to observe MChA measures the difference in luminescence intensity in the directions parallel and antiparallel to B [17,18]. In order to increase sensitivity, the magnetic field is alternated and the intensity difference 1B k is phase-sensitively detected by a... 

Study of the intensity and splitting pattern of certain transitions in the fluorescence spectra of compounds of Eu + and Tb in particular can give a good deal of information about the environment of the lanthanide ion. The mles are summarized in Tables 5.4 and 5.5 for both europium and terbium. Owing to the weakness of the electric dipole transitions, the magnetic dipole transitions are of comparable intensity. (For Eu +, Dq are... 

The temperature dependence of the internal magnetic field in europium metal shows a sudden collapse at 88-5 K where a first-order phase transition causes the field to fall from 40% of the saturation value to zero [51]. 

Fig. 6.15(b). The magnetic moment of europium measured in a field of 1.2 T as a function of temperature near Tn- The ordering transition is first-order (after McEwen and Touborg 1971). 

The orthorhombic EuH2 is (like YbH2) an insulator, since the divalent europium has lost both its valence electrons upon hydriding. The Eu ion has seven uiq>aired spins and is strongly magnetic, resulting in a FM transition at Tc 16-18K (Mustachi 1974, Bischof et al. 1983, Drulis and Stalinski 1989, Drulis 1993). 

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