Hyperfine Fields and Isomer Shifts in Magnetically Ordered Europium Compounds

The Mössbauer technique was employed to study hyperfine fields in several ordered divalent europium compounds at low temperatures. The intermetallics EuCu2, EuAl2, and EuAl4 were ordered at helium temperatures and the observed fields and isomer shifts were 189(8) kOe, −0.88 cm/sec; 278(8) kOe, −0.97 cm/sec; and 290(8) kOe, −1.14 cm/sec, respectively. Comparison of these results and previous measurements with EuO, EuS, and Eu metal indicates a possible correlation between isomer shift and internal field. With the exception of EuCu2 the internal fields increase with increasing magnitude of isomer shift. Interpretation of this trend with a core polarization model yields a value of 120±20 kOe for the field per 6s valence electron.

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