Magnetic-dilution in the solid solutions Eu1−xCaxPtSn and Eu1−xSrxPtSn – crystal structure, magnetism, and 151Eu and 119Sn Mössbauer spectroscopy

Abstract

The TiNiSi-type stannide EuPtSn (space group Pnma) forms complete solid solutions with the isotypic compounds CaPtSn and SrPtSn. Samples in 10 mol% steps with composition Eu_1−xCa_xPtSn and Eu_1−xSr_xPtSn (0 ≤ x ≤ 1) were synthesized and studied by X-ray powder diffraction, magnetization, and ¹⁵¹Eu and ¹¹⁹Sn Mössbauer spectroscopy measurements. The cell volumes decrease with increasing calcium content and increase with strontium substitution. The crystal structures of CaPtSn, Eu_0.606(2)Ca_0.394Pt_0.987(4)Sn_1.013 and Eu_0.426(4)Sr_0.574PtSn were refined from single crystal X-ray diffraction data, confirming their TiNiSi-type structure and the mixed occupancies Eu/Ca, respectively Eu/Sr. Temperature dependent magnetic susceptibility measurements show diamagnetism for the border phases CaPtSn and SrPtSn. The Eu_1−xCa_xPtSn and Eu_1−xSr_xPtSn samples show all stable divalent ground states with experimental magnetic moments close to the free ion value of 7.94µ_B for Eu²⁺. This finding is also corroborated by ¹⁵¹Eu Mössbauer spectroscopy. The compounds order antiferromagnetically at low temperatures. The stable antiferromagnetic ground state is underpinned by their metamagnetic (AFM → FM) transitions. A remarkable feature is the linear decrease of the Néel temperature, T_N, in both solid solutions Eu_1−xCa_xPtSn and Eu_1−xSr_xPtSn, from 28.5 K (EuPtSn) to 3.2(1) K for Eu_0.2Ca_0.8PtSn and 3.4(1) K for Eu_0.2Sr_0.8PtSn. The decrease of the Néel temperature is continuous, however with slightly different slopes for Ca and Sr substitution.