The System EuSe-LaSe

Solid solutions of the continuous series Eu. LaxSe (of the NaCl type, Holtzberg et al. [1]) are prepared from appropriate finely powdered mixtures of EuSe and LaSe by heating the pellets in a sealed Ta crucible at 2000 to 2500°C for 10 to 20 min, Holtzberg etal. [2]. The decrease of the lattice parameter from a = 6.20 A in EuSe to 6.08 A in LaSe is for Eu-rich samples (x 0.5) less than expected from Vegard s law. The paramagnetic Curie temperature increases as a function of x from 0p = 1O K in EuSe to a broad maximum with p = 30 at x = 0.25 (cf. [2]) 0p decreases between x = 0.4 and 0.95 from 22 to 10 K [1]. 

For La-doped EuSe samples with x 0.04, Eu Mossbauer spectra between 1.5 and 4.2 K yield a temperature dependence of the hyperfine field at the Eu nuclei, Heff, which deviates significantly from the temperature dependence of pure EuSe, indicating some change in the magnetic structure. (EuSe is antiferromagnetic AF-NNSS above 2.8 K, ferrimagnetic NNS 

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