A Europium-151 Mössbauer Spectral Study of Eu 14 MnP 11 , Eu 14 MnAs 11 , and Eu 14 MnSb 11

The europium-151 Mossbauer spectra of the Eu 1 4 MnP 1 1 , Eu 1 4 MnAs 1 1 , and Eu 1 4 MnSb 1 1 Zintl compounds, measured between 4.2 and 100 K, reveal europium(II) for all four crystallographically inequivalent europium sites in Eu 1 4 MnAs 1 1 and Eu 1 4 MnSb 1 1 and europium(II) and europium(III) for the three 32g and the 16f europium sites in Eu 1 4 MnP 1 1 , respectively. Below the ordering temperatures of 52, 74, and 92 K, only very small hyperfine fields of 2-4 T are observed at the europium sites as a result of the polarization by the manganese magnetic moments. At 4.2 K, the europium(II) magnetic moments are ordered, and hyperfine fields of 24.4, 24.8, and 19.3 T are observed in Eu 1 4 MnP 1 1 , Eu 1 4 MnAs 1 1 , and Eu 1 4 MnSb 1 1 , respectively, fields that are typical for magnetically ordered europium(II) ions. At 4.2 K the 16f europium(III) sites in Eu 1 4 MnP 1 1 experience a transferred hyperfine field of 33 T from the neighboring ordered europium(II) moments. Between its Curie temperature and 4.2 K, the europium-151 Mossbauer spectra of Eu 1 4 MnSb 1 1 reveal that the europium(II) moments order below ca. 13 K, i.e., below the second magnetic transition observed in magnetic measurements. Between their Curie temperatures and 4.2 K, the europium-151 Mossbauer spectra of Eu 1 4 MnP 1 1 and Eu 1 4 MnAs 1 1 are complex and have been analyzed with two models, models that give equivalently good fits. However, the second model in which the spectra are fit with a three-dimensional relaxation of the europium(II) and europium(III) hyperfine fields is preferred for its physical meaning and its reduced number of fitted parameters.